21939890 has 64 divisors (see below), whose sum is σ = 47672064. Its totient is φ = 7112448.

The previous prime is 21939881. The next prime is 21939919. The reversal of 21939890 is 9893912.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 111272 + ... + 111468.

It is an arithmetic number, because the mean of its divisors is an integer number (744876).

Almost surely, 2^21939890 is an apocalyptic number.

21939890 is an abundant number, since it is smaller than the sum of its proper divisors (25732174).

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

21939890 is a wasteful number, since it uses less digits than its factorization.

21939890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 291.

The product of its (nonzero) digits is 34992, while the sum is 41.

The square root of 21939890 is about 4684.0036293752. The cubic root of 21939890 is about 279.9485024339.

The spelling of 21939890 in words is "twenty-one million, nine hundred thirty-nine thousand, eight hundred ninety".