21660625 has 20 divisors (see below), whose sum is σ = 30940096. Its totient is φ = 14850000.

The previous prime is 21660619. The next prime is 21660637. The reversal of 21660625 is 52606612.

It is not a de Polignac number, because 21660625 - 2¹⁷ = 21529553 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21660593 and 21660602.

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 19 ways as a sum of consecutive naturals, for example, 1900 + ... + 6850.

Almost surely, 2^21660625 is an apocalyptic number.

21660625 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

21660625 is a deficient number, since it is larger than the sum of its proper divisors (9279471).

21660625 is an frugal number, since it uses more digits than its factorization.

21660625 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4978 (or 4963 counting only the distinct ones).

The product of its (nonzero) digits is 4320, while the sum is 28.

The square root of 21660625 is about 4654.0976569041. The cubic root of 21660625 is about 278.7556387821.

The spelling of 21660625 in words is "twenty-one million, six hundred sixty thousand, six hundred twenty-five".