SHA-1哈希可以纯粹是数字吗？

Question

Is there any chance that a SHA-1 hash can be purely numeric, or does the algorithm ensure that there must be at least one alphabetical character?

Edit: I'm representing it in base 16, as a string returned by PHP's sha1() function.

Answer 1

technically, a SHA1 hash is a number, it is just most often encoded in base 16 (which is what PHP's sha1() does) so that it nearly always has a letter in it. There is no guarantee of this though.

The odds of a hex encoded 160 bit number having no digits A-F are (10/16)⁴⁰ or about 6.84227766 × 10^-9