21705868 has 6 divisors (see below), whose sum is σ = 37985276. Its totient is φ = 10852932.

The previous prime is 21705863. The next prime is 21705883. The reversal of 21705868 is 86850712.

It is a super-2 number, since 2×21705868² = 942289411266848, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21705863) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2713230 + ... + 2713237.

Almost surely, 2^21705868 is an apocalyptic number.

It is an amenable number.

21705868 is a deficient number, since it is larger than the sum of its proper divisors (16279408).

21705868 is a wasteful number, since it uses less digits than its factorization.

21705868 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5426471 (or 5426469 counting only the distinct ones).

The product of its (nonzero) digits is 26880, while the sum is 37.

The square root of 21705868 is about 4658.9556769731. The cubic root of 21705868 is about 278.9495847207.

The spelling of 21705868 in words is "twenty-one million, seven hundred five thousand, eight hundred sixty-eight".