21659868 has 36 divisors (see below), whose sum is σ = 56642040. Its totient is φ = 6970656.

The previous prime is 21659863. The next prime is 21659873. The reversal of 21659868 is 86895612.

It is an interprime number because it is at equal distance from previous prime (21659863) and next prime (21659873).

It is a tau number, because it is divible by the number of its divisors (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21659863) 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, 9330 + ... + 11417.

It is an arithmetic number, because the mean of its divisors is an integer number (1573390).

Almost surely, 2^21659868 is an apocalyptic number.

It is an amenable number.

21659868 is an abundant number, since it is smaller than the sum of its proper divisors (34982172).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21659868 is a wasteful number, since it uses less digits than its factorization.

21659868 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20786 (or 20781 counting only the distinct ones).

The product of its digits is 207360, while the sum is 45.

The square root of 21659868 is about 4654.0163300100. The cubic root of 21659868 is about 278.7523914077.

The spelling of 21659868 in words is "twenty-one million, six hundred fifty-nine thousand, eight hundred sixty-eight".