21665412 has 36 divisors (see below), whose sum is σ = 57988476. Its totient is φ = 6796800.

The previous prime is 21665401. The next prime is 21665473. The reversal of 21665412 is 21456612.

21665412 is a `hidden beast` number, since 2 + 1 + 6 + 654 + 1 + 2 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 10536516 + 11128896 = 3246^2 + 3336^2 .

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

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 17089 + ... + 18312.

It is an arithmetic number, because the mean of its divisors is an integer number (1610791).

Almost surely, 2^21665412 is an apocalyptic number.

It is an amenable number.

21665412 is an abundant number, since it is smaller than the sum of its proper divisors (36323064).

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

21665412 is a wasteful number, since it uses less digits than its factorization.

21665412 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 35428 (or 35423 counting only the distinct ones).

The product of its digits is 2880, while the sum is 27.

The square root of 21665412 is about 4654.6119064859. The cubic root of 21665412 is about 278.7761722763.

The spelling of 21665412 in words is "twenty-one million, six hundred sixty-five thousand, four hundred twelve".