21566725 has 6 divisors (see below), whose sum is σ = 26742770. Its totient is φ = 17253360.

The previous prime is 21566719. The next prime is 21566737. The reversal of 21566725 is 52766512.

It can be written as a sum of positive squares in 3 ways, for example, as 277729 + 21288996 = 527^2 + 4614^2 .

It is a de Polignac number, because none of the positive numbers 2^k-21566725 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 431310 + ... + 431359.

Almost surely, 2^21566725 is an apocalyptic number.

21566725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21566725 is a deficient number, since it is larger than the sum of its proper divisors (5176045).

21566725 is an equidigital number, since it uses as much as digits as its factorization.

21566725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 862679 (or 862674 counting only the distinct ones).

The product of its digits is 25200, while the sum is 34.

The square root of 21566725 is about 4643.9988156760. The cubic root of 21566725 is about 278.3522483072.

The spelling of 21566725 in words is "twenty-one million, five hundred sixty-six thousand, seven hundred twenty-five".