21945868 has 12 divisors (see below), whose sum is σ = 43891792. Its totient is φ = 9405360.

The previous prime is 21945863. The next prime is 21945871. The reversal of 21945868 is 86854912.

It is a happy number.

21945868 is an admirable number.

It is a super-2 number, since 2×21945868² = 963242244546848, which contains 22 as substring.

It is a hoax number, since the sum of its digits (43) coincides with the sum of the digits of its distinct prime factors.

It is not an unprimeable number, because it can be changed into a prime (21945863) 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 in 3 ways as a sum of consecutive naturals, for example, 391863 + ... + 391918.

Almost surely, 2^21945868 is an apocalyptic number.

21945868 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21945868 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

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

21945868 is a wasteful number, since it uses less digits than its factorization.

21945868 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 783792 (or 783790 counting only the distinct ones).

The product of its digits is 138240, while the sum is 43.

The square root of 21945868 is about 4684.6417152222. The cubic root of 21945868 is about 279.9739261435.

The spelling of 21945868 in words is "twenty-one million, nine hundred forty-five thousand, eight hundred sixty-eight".