21523725 has 42 divisors (see below), whose sum is σ = 40049706. Its totient is φ = 11469600.

The previous prime is 21523681. The next prime is 21523727. The reversal of 21523725 is 52732512.

It can be written as a sum of positive squares in 3 ways, for example, as 4901796 + 16621929 = 2214^2 + 4077^2 .

It is not a de Polignac number, because 21523725 - 2¹⁰ = 21522701 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21523727) by changing a digit.

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 41 ways as a sum of consecutive naturals, for example, 17635 + ... + 18815.

Almost surely, 2^21523725 is an apocalyptic number.

21523725 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21523725 is a deficient number, since it is larger than the sum of its proper divisors (18525981).

21523725 is an equidigital number, since it uses as much as digits as its factorization.

21523725 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1209 (or 1189 counting only the distinct ones).

The product of its digits is 4200, while the sum is 27.

The square root of 21523725 is about 4639.3668749087. The cubic root of 21523725 is about 278.1671311843.

The spelling of 21523725 in words is "twenty-one million, five hundred twenty-three thousand, seven hundred twenty-five".