21664026 has 12 divisors (see below), whose sum is σ = 46938762. Its totient is φ = 7221336.

The previous prime is 21664007. The next prime is 21664037. The reversal of 21664026 is 62046612.

It is a happy number.

21664026 is a `hidden beast` number, since 2 + 16 + 640 + 2 + 6 = 666.

It can be written as a sum of positive squares in only one way, i.e., 19368801 + 2295225 = 4401^2 + 1515^2 .

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 601761 + ... + 601796.

Almost surely, 2^21664026 is an apocalyptic number.

21664026 is an abundant number, since it is smaller than the sum of its proper divisors (25274736).

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

21664026 is a wasteful number, since it uses less digits than its factorization.

21664026 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1203565 (or 1203562 counting only the distinct ones).

The product of its (nonzero) digits is 3456, while the sum is 27.

The square root of 21664026 is about 4654.4630195115. The cubic root of 21664026 is about 278.7702274395.

The spelling of 21664026 in words is "twenty-one million, six hundred sixty-four thousand, twenty-six".