21664894 has 4 divisors (see below), whose sum is σ = 32497344. Its totient is φ = 10832446.

The previous prime is 21664891. The next prime is 21664897. The reversal of 21664894 is 49846612.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (21664891) and next prime (21664897).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21664891) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5416222 + ... + 5416225.

It is an arithmetic number, because the mean of its divisors is an integer number (8124336).

Almost surely, 2^21664894 is an apocalyptic number.

21664894 is a deficient number, since it is larger than the sum of its proper divisors (10832450).

21664894 is a wasteful number, since it uses less digits than its factorization.

21664894 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10832449.

The product of its digits is 82944, while the sum is 40.

The square root of 21664894 is about 4654.5562624164. The cubic root of 21664894 is about 278.7739504983.

The spelling of 21664894 in words is "twenty-one million, six hundred sixty-four thousand, eight hundred ninety-four".