21739890 has 32 divisors (see below), whose sum is σ = 52301376. Its totient is φ = 5783360.

The previous prime is 21739877. The next prime is 21739903. The reversal of 21739890 is 9893712.

It is an interprime number because it is at equal distance from previous prime (21739877) and next prime (21739903).

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19960 + ... + 21020.

It is an arithmetic number, because the mean of its divisors is an integer number (1634418).

Almost surely, 2^21739890 is an apocalyptic number.

21739890 is an abundant number, since it is smaller than the sum of its proper divisors (30561486).

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

21739890 is a wasteful number, since it uses less digits than its factorization.

21739890 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1754.

The product of its (nonzero) digits is 27216, while the sum is 39.

The square root of 21739890 is about 4662.6054947851. The cubic root of 21739890 is about 279.0952514535.

The spelling of 21739890 in words is "twenty-one million, seven hundred thirty-nine thousand, eight hundred ninety".