21815625 has 48 divisors (see below), whose sum is σ = 39372480. Its totient is φ = 10680000.

The previous prime is 21815617. The next prime is 21815639. The reversal of 21815625 is 52651812.

It is not a de Polignac number, because 21815625 - 2³ = 21815617 is a prime.

Its product of digits (4800) is a multiple of the sum of its prime divisors (200).

It is a junction number, because it is equal to n+sod(n) for n = 21815592 and 21815601.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 121786 + ... + 121964.

It is an arithmetic number, because the mean of its divisors is an integer number (820260).

Almost surely, 2^21815625 is an apocalyptic number.

21815625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21815625 is a deficient number, since it is larger than the sum of its proper divisors (17556855).

21815625 is an equidigital number, since it uses as much as digits as its factorization.

21815625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 220 (or 200 counting only the distinct ones).

The product of its digits is 4800, while the sum is 30.

The square root of 21815625 is about 4670.7199659153. The cubic root of 21815625 is about 279.4189694519.

The spelling of 21815625 in words is "twenty-one million, eight hundred fifteen thousand, six hundred twenty-five".