21756868 has 12 divisors (see below), whose sum is σ = 43513792. Its totient is φ = 9324360.

The previous prime is 21756863. The next prime is 21756883. The reversal of 21756868 is 86865712.

21756868 is an admirable number.

It is a super-2 number, since 2×21756868² = 946722610338848, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (21756863) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 388488 + ... + 388543.

Almost surely, 2^21756868 is an apocalyptic number.

21756868 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21756868 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.

21756868 is a wasteful number, since it uses less digits than its factorization.

21756868 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 777042 (or 777040 counting only the distinct ones).

The product of its digits is 161280, while the sum is 43.

The square root of 21756868 is about 4664.4257953150. The cubic root of 21756868 is about 279.1678866905.

The spelling of 21756868 in words is "twenty-one million, seven hundred fifty-six thousand, eight hundred sixty-eight".