Blockchain-based currencies use encoded strings, which are a Base58Check encoding of some hash, typically that of a public key. The encoding includes a prefix (traditionally a single version byte), which affects the leading symbol(s) in the encoded result. The following is a list of some prefixes which are in use in the reference Bitcoin codebase. (1.1) (1.2)

Decimal prefix Hex Example use Leading symbol(s) Example
0 00 Pubkey hash (P2PKH address) 1 17VZNX1SN5NtKa8UQFxwQbFeFc3iqRYhem
5 05 Script hash (P2SH address) 3 3EktnHQD7RiAE6uzMj2ZifT9YgRrkSgzQX
128 80 Private key (WIF, uncompressed pubkey) 5 5Hwgr3u458GLafKBgxtssHSPqJnYoGrSzgQsPwLFhLNYskDPyyA
128 80 Private key (WIF, compressed pubkey) K orL L1aW4aubDFB7yfras2S1mN3bqg9nwySY8nkoLmJebSLD5BWv3ENZ
4 136 178 30 0488B21E BIP32pubkey xpub xpub661MyMwAqRbcEYS8w7XLSVeEsBXy79zSzH1J8vCdxAZningWLdN3zgtU6LBpB85b3D2yc8sfvZU521AAwdZafEz7mnzBBsz4wKY5e4cp9LB
4 136 173 228 0488ADE4 BIP32 private key xprv xprv9s21ZrQH143K24Mfq5zL5MhWK9hUhhGbd45hLXo2Pq2oqzMMo63oStZzF93Y5wvzdUayhgkkFoicQZcP3y52uPPxFnfoLZB21Teqt1VvEHx
111 6F Testnet pubkey hash m orn mipcBbFg9gMiCh81Kj8tqqdgoZub1ZJRfn
196 C4 Testnet script hash 2 2MzQwSSnBHWHqSAqtTVQ6v47XtaisrJa1Vc
239 EF Testnet Private key (WIF, uncompressed pubkey) 9 92Pg46rUhgTT7romnV7iGW6W1gbGdeezqdbJCzShkCsYNzyyNcc
239 EF Testnet Private key (WIF, compressed pubkey) c cNJFgo1driFnPcBdBX8BrJrpxchBWXwXCvNH5SoSkdcF6JXXwHMm
4 53 135 207 043587CF Testnet BIP32 pubkey tpub tpubD6NzVbkrYhZ4WLczPJWReQycCJdd6YVWXubbVUFnJ5KgU5MDQrD998ZJLNGbhd2pq7ZtDiPYTfJ7iBenLVQpYgSQqPjUsQeJXH8VQ8xA67D
4 53 131 148 04358394 Testnet BIP32 private key tprv tprv8ZgxMBicQKsPcsbCVeqqF1KVdH7gwDJbxbzpCxDUsoXHdb6SnTPYxdwSAKDC6KKJzv7khnNWRAJQsRA8BBQyiSfYnRt6zuu4vZQGKjeW4YF

Note that private keys for compressed and uncompressed bitcoin public keys use the same version byte. The reason for the compressed form starting with a different character is because a 0x01 byte is appended to the private key before base58 encoding.

The following table shows the leading symbol(s) and address length(s) for 160 bit hashes for each of the possible decimal version values:

Decimal version Leading symbol Address length
0 1 up to 34
1 Q-Z, a-k, m-o 33
2 o-z, 2 33 or 34
3 2 34
4 2 or 3 34
5-6 3 34
7 3 or 4 34
8 4 34
9 4 or 5 34
10-11 5 34
12 5 or 6 34
13 6 34
14 6 or 7 34
15-16 7 34
17 7 or 8 34
18 8 34
19 8 or 9 34
20-21 9 34
22 9 or A 34
23 A 34
24 A or B 34
25-26 B 34
27 B or C 34
28 C 34
29 C or D 34
30-31 D 34
32 D or E 34
33 E 34
34 E or F 34
35-36 F 34
37 F or G 34
38 G 34
39 G or H 34
40-41 H 34
42 H or J 34
43 J 34
44 J or K 34
45-46 K 34
47 K or L 34
48 L 34
49 L or M 34
50-51 M 34
52 M or N 34
53 N 34
54 N or P 34
55-56 P 34
57 P or Q 34
58 Q 34
59 Q or R 34
60-61 R 34
62 R or S 34
63 S 34
64 S or T 34
65-66 T 34
67 T or U 34
68 U 34
69 U or V 34
70-71 V 34
72 V or W 34
73 W 34
74 W or X 34
75-76 X 34
77 X or Y 34
78 Y 34
79 Y or Z 34
80-81 Z 34
82 Z or a 34
83 a 34
84 a or b 34
85 b 34
86 b or c 34
87-88 c 34
89 c or d 34
90 d 34
91 d or e 34
92-93 e 34
94 e or f 34
95 f 34
96 f or g 34
97-98 g 34
99 g or h 34
100 h 34
101 h or i 34
102-103 i 34
104 i or j 34
105 j 34
106 j or k 34
107-108 k 34
109 k or m 34
110 m 34
111 m or n 34
112-113 n 34
114 n or o 34
115 o 34
116 o or p 34
117-118 p 34
119 p or q 34
120 q 34
121 q or r 34
122-123 r 34
124 r or s 34
125 s 34
126 s or t 34
127-128 t 34
129 t or u 34
130 u 34
131 u or v 34
132-133 v 34
134 v or w 34
135 w 34
136 w or x 34
137-138 x 34
139 x or y 34
140 y 34
141 y or z 34
142-143 z 34
144 z or 2 34 or 35
145-255 2 35

References

1.1: https://github.com/bitcoin/bitcoin/blob/master/src/chainparams.cpp#L159-163
1.2: https://github.com/bitcoin/bitcoin/blob/master/src/chainparams.cpp#L217-221