Syntax:
CONV(N,from_base,to_base)

Converts numbers between different number bases. Returns a string
representation of the number N, converted from base from_base to base
to_base. Returns NULL if any argument is NULL. The argument N is
interpreted as an integer, but may be specified as an integer or a
string. The minimum base is 2 and the maximum base is 36. If from_base
is a negative number, N is regarded as a signed number. Otherwise, N is
treated as unsigned. CONV() works with 64-bit precision.

URL: https://dev.mysql.com/doc/refman/5.7/en/mathematical-functions.html

