21664770 has 16 divisors (see below), whose sum is σ = 51995520. Its totient is φ = 5777264.

The previous prime is 21664763. The next prime is 21664771. The reversal of 21664770 is 7746612.

It is not an unprimeable number, because it can be changed into a prime (21664771) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 361050 + ... + 361109.

It is an arithmetic number, because the mean of its divisors is an integer number (3249720).

Almost surely, 2^21664770 is an apocalyptic number.

21664770 is an abundant number, since it is smaller than the sum of its proper divisors (30330750).

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

21664770 is a wasteful number, since it uses less digits than its factorization.

21664770 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 722169.

The product of its (nonzero) digits is 14112, while the sum is 33.

The square root of 21664770 is about 4654.5429421158. The cubic root of 21664770 is about 278.7734186388.

The spelling of 21664770 in words is "twenty-one million, six hundred sixty-four thousand, seven hundred seventy".