21639384 has 96 divisors (see below), whose sum is σ = 64318800. Its totient is φ = 6531840.

The previous prime is 21639383. The next prime is 21639427. The reversal of 21639384 is 48393612.

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 not an unprimeable number, because it can be changed into a prime (21639383) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 56907 + ... + 57285.

Almost surely, 2^21639384 is an apocalyptic number.

21639384 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 21639384, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (32159400).

21639384 is an abundant number, since it is smaller than the sum of its proper divisors (42679416).

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

21639384 is a wasteful number, since it uses less digits than its factorization.

21639384 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 465 (or 458 counting only the distinct ones).

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

The square root of 21639384 is about 4651.8151296026. The cubic root of 21639384 is about 278.6644905192.

The spelling of 21639384 in words is "twenty-one million, six hundred thirty-nine thousand, three hundred eighty-four".