21947864 has 8 divisors (see below), whose sum is σ = 41152260. Its totient is φ = 10973928.

The previous prime is 21947857. The next prime is 21947897. The reversal of 21947864 is 46874912.

It is a tau number, because it is divible by the number of its divisors (8).

It is a super-3 number, since 3×21947864³ (a number of 23 digits) contains 333 as substring.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1371734 + ... + 1371749.

Almost surely, 2^21947864 is an apocalyptic number.

It is an amenable number.

21947864 is a deficient number, since it is larger than the sum of its proper divisors (19204396).

21947864 is a wasteful number, since it uses less digits than its factorization.

21947864 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2743489 (or 2743485 counting only the distinct ones).

The product of its digits is 96768, while the sum is 41.

The square root of 21947864 is about 4684.8547469479. The cubic root of 21947864 is about 279.9824138615.

The spelling of 21947864 in words is "twenty-one million, nine hundred forty-seven thousand, eight hundred sixty-four".