21639324 has 24 divisors (see below), whose sum is σ = 57705088. Its totient is φ = 6182640.

The previous prime is 21639313. The next prime is 21639329. The reversal of 21639324 is 42393612.

It is a junction number, because it is equal to n+sod(n) for n = 21639291 and 21639300.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21639329) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 128722 + ... + 128889.

Almost surely, 2^21639324 is an apocalyptic number.

It is an amenable number.

21639324 is an abundant number, since it is smaller than the sum of its proper divisors (36065764).

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

21639324 is a wasteful number, since it uses less digits than its factorization.

21639324 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 257625 (or 257623 counting only the distinct ones).

The product of its digits is 7776, while the sum is 30.

The square root of 21639324 is about 4651.8086805027. The cubic root of 21639324 is about 278.6642329659.

The spelling of 21639324 in words is "twenty-one million, six hundred thirty-nine thousand, three hundred twenty-four".