It is a happy number.
15624 is nontrivially palindromic in base 5.
15624 is a nontrivial repdigit in base 5.
It is a plaindrome in base 5.
It is a nialpdrome in base 5.
It is a zygodrome in base 5.
It is a congruent number.
Being equal to 5×55-1, it is a generalized Woodall number.
15624 is an untouchable number, because it is not equal to the sum of proper divisors of any number.
15624 is a Friedman number, since it can be written as 5^(4+2)-1^6, using all its digits and the basic arithmetic operations.
215624 is an apocalyptic number.
15624 is a gapful number since it is divisible by the number (14) formed by its first and last digit.
It is an amenable number.
It is a practical number, because each smaller number is the sum of distinct divisors of 15624, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24960).
It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.
15624 is a wasteful number, since it uses less digits than its factorization.
15624 is an evil number, because the sum of its binary digits is even.
The square root of 15624 is about 124.9959999360. The cubic root of 15624 is about 24.9994666553. Note that the first 3 decimals are identical.
The spelling of 15624 in words is "fifteen thousand, six hundred twenty-four".