21557925 has 18 divisors (see below), whose sum is σ = 38613042. Its totient is φ = 11497440.

The previous prime is 21557917. The next prime is 21557941. The reversal of 21557925 is 52975512.

It can be written as a sum of positive squares in 3 ways, for example, as 19044 + 21538881 = 138^2 + 4641^2 .

It is not a de Polignac number, because 21557925 - 2³ = 21557917 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21557925.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 17 ways as a sum of consecutive naturals, for example, 47682 + ... + 48131.

It is an arithmetic number, because the mean of its divisors is an integer number (2145169).

Almost surely, 2^21557925 is an apocalyptic number.

21557925 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21557925 is a deficient number, since it is larger than the sum of its proper divisors (17055117).

21557925 is a wasteful number, since it uses less digits than its factorization.

21557925 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 95829 (or 95821 counting only the distinct ones).

The product of its digits is 31500, while the sum is 36.

The square root of 21557925 is about 4643.0512596783. The cubic root of 21557925 is about 278.3143839116.

The spelling of 21557925 in words is "twenty-one million, five hundred fifty-seven thousand, nine hundred twenty-five".