21664701 has 6 divisors (see below), whose sum is σ = 31293470. Its totient is φ = 14443128.

The previous prime is 21664667. The next prime is 21664703. The reversal of 21664701 is 10746612.

21664701 is a `hidden beast` number, since 2 + 16 + 647 + 0 + 1 = 666.

It can be written as a sum of positive squares in only one way, i.e., 21483225 + 181476 = 4635^2 + 426^2 .

It is not a de Polignac number, because 21664701 - 2⁶ = 21664637 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21664703) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 1203586 + ... + 1203603.

Almost surely, 2^21664701 is an apocalyptic number.

It is an amenable number.

21664701 is a deficient number, since it is larger than the sum of its proper divisors (9628769).

21664701 is a wasteful number, since it uses less digits than its factorization.

21664701 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2407195 (or 2407192 counting only the distinct ones).

The product of its (nonzero) digits is 2016, while the sum is 27.

The square root of 21664701 is about 4654.5355299965. The cubic root of 21664701 is about 278.7731226839.

The spelling of 21664701 in words is "twenty-one million, six hundred sixty-four thousand, seven hundred one".