21420868 has 12 divisors (see below), whose sum is σ = 42841792. Its totient is φ = 9180360.

The previous prime is 21420863. The next prime is 21420881. The reversal of 21420868 is 86802412.

21420868 is an admirable number.

It is a hoax number, since the sum of its digits (31) 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 (21420863) 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, 382488 + ... + 382543.

Almost surely, 2^21420868 is an apocalyptic number.

21420868 is a gapful number since it is divisible by the number (28) formed by its first and last digit.

It is an amenable number.

21420868 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.

21420868 is a wasteful number, since it uses less digits than its factorization.

21420868 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 765042 (or 765040 counting only the distinct ones).

The product of its (nonzero) digits is 6144, while the sum is 31.

The square root of 21420868 is about 4628.2683586845. The cubic root of 21420868 is about 277.7233242712.

The spelling of 21420868 in words is "twenty-one million, four hundred twenty thousand, eight hundred sixty-eight".