21339864 has 96 divisors (see below), whose sum is σ = 71154720. Its totient is φ = 5626368.

The previous prime is 21339859. The next prime is 21339889. The reversal of 21339864 is 46893312.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

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 23 ways as a sum of consecutive naturals, for example, 4924 + ... + 8180.

It is an arithmetic number, because the mean of its divisors is an integer number (741195).

Almost surely, 2^21339864 is an apocalyptic number.

21339864 is a gapful number since it is divisible by the number (24) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21339864, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (35577360).

21339864 is an abundant number, since it is smaller than the sum of its proper divisors (49814856).

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

21339864 is a wasteful number, since it uses less digits than its factorization.

21339864 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3289 (or 3282 counting only the distinct ones).

The product of its digits is 31104, while the sum is 36.

The square root of 21339864 is about 4619.5090648250. The cubic root of 21339864 is about 277.3728075489.

The spelling of 21339864 in words is "twenty-one million, three hundred thirty-nine thousand, eight hundred sixty-four".