21390858 has 32 divisors (see below), whose sum is σ = 47822400. Its totient is φ = 7087248.

The previous prime is 21390857. The next prime is 21390871. The reversal of 21390858 is 85809312.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is not an unprimeable number, because it can be changed into a prime (21390857) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 8560 + ... + 10772.

It is an arithmetic number, because the mean of its divisors is an integer number (1494450).

Almost surely, 2^21390858 is an apocalyptic number.

21390858 is an abundant number, since it is smaller than the sum of its proper divisors (26431542).

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

21390858 is a wasteful number, since it uses less digits than its factorization.

21390858 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2403 (or 2397 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 36.

The square root of 21390858 is about 4625.0251891206. The cubic root of 21390858 is about 277.5935696147.

The spelling of 21390858 in words is "twenty-one million, three hundred ninety thousand, eight hundred fifty-eight".