21939588 has 72 divisors (see below), whose sum is σ = 64078560. Its totient is φ = 6255360.

The previous prime is 21939581. The next prime is 21939607. The reversal of 21939588 is 88593912.

It is a happy number.

It is not an unprimeable number, because it can be changed into a prime (21939581) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 5103 + ... + 8361.

It is an arithmetic number, because the mean of its divisors is an integer number (889980).

Almost surely, 2^21939588 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21939588, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32039280).

21939588 is an abundant number, since it is smaller than the sum of its proper divisors (42138972).

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

21939588 is a wasteful number, since it uses less digits than its factorization.

21939588 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3297 (or 3292 counting only the distinct ones).

The product of its digits is 155520, while the sum is 45.

The square root of 21939588 is about 4683.9713918853. The cubic root of 21939588 is about 279.9472179420.

It can be divided in two parts, 2193 and 9588, that added together give a triangular number (11781 = T₁₅₃).

The spelling of 21939588 in words is "twenty-one million, nine hundred thirty-nine thousand, five hundred eighty-eight".