21390860 has 12 divisors (see below), whose sum is σ = 44920848. Its totient is φ = 8556336.

The previous prime is 21390857. The next prime is 21390871. The reversal of 21390860 is 6809312.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 534752 + ... + 534791.

It is an arithmetic number, because the mean of its divisors is an integer number (3743404).

Almost surely, 2^21390860 is an apocalyptic number.

21390860 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21390860 is an abundant number, since it is smaller than the sum of its proper divisors (23529988).

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

21390860 is a wasteful number, since it uses less digits than its factorization.

21390860 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1069552 (or 1069550 counting only the distinct ones).

The product of its (nonzero) digits is 2592, while the sum is 29.

The square root of 21390860 is about 4625.0254053356. The cubic root of 21390860 is about 277.5935782661.

The spelling of 21390860 in words is "twenty-one million, three hundred ninety thousand, eight hundred sixty".