21520825 has 12 divisors (see below), whose sum is σ = 28090960. Its totient is φ = 16310160.

The previous prime is 21520799. The next prime is 21520831. The reversal of 21520825 is 52802512.

It is a de Polignac number, because none of the positive numbers 2^k-21520825 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (25).

It is a self number, because there is not a number n which added to its sum of digits gives 21520825.

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 11 ways as a sum of consecutive naturals, for example, 22179 + ... + 23128.

Almost surely, 2^21520825 is an apocalyptic number.

21520825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21520825 is a deficient number, since it is larger than the sum of its proper divisors (6570135).

21520825 is a wasteful number, since it uses less digits than its factorization.

21520825 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 45336 (or 45331 counting only the distinct ones).

The product of its (nonzero) digits is 1600, while the sum is 25.

The square root of 21520825 is about 4639.0543217341. The cubic root of 21520825 is about 278.1546376698.

The spelling of 21520825 in words is "twenty-one million, five hundred twenty thousand, eight hundred twenty-five".