21687925 has 12 divisors (see below), whose sum is σ = 30735136. Its totient is φ = 14871600.

The previous prime is 21687923. The next prime is 21687931. The reversal of 21687925 is 52978612.

It is not a de Polignac number, because 21687925 - 2¹ = 21687923 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21687923) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 61791 + ... + 62140.

Almost surely, 2^21687925 is an apocalyptic number.

21687925 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21687925 is a deficient number, since it is larger than the sum of its proper divisors (9047211).

21687925 is a wasteful number, since it uses less digits than its factorization.

21687925 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 123948 (or 123943 counting only the distinct ones).

The product of its digits is 60480, while the sum is 40.

The square root of 21687925 is about 4657.0296327165. The cubic root of 21687925 is about 278.8726996405.

The spelling of 21687925 in words is "twenty-one million, six hundred eighty-seven thousand, nine hundred twenty-five".