21539680 has 48 divisors (see below), whose sum is σ = 53887680. Its totient is φ = 8108032.

The previous prime is 21539671. The next prime is 21539681. The reversal of 21539680 is 8693512.

It is a Harshad number since it is a multiple of its sum of digits (34).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21539681) 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, 1240 + ... + 6679.

It is an arithmetic number, because the mean of its divisors is an integer number (1122660).

Almost surely, 2^21539680 is an apocalyptic number.

21539680 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21539680 is an abundant number, since it is smaller than the sum of its proper divisors (32348000).

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

21539680 is a wasteful number, since it uses less digits than its factorization.

21539680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7951 (or 7943 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 34.

The square root of 21539680 is about 4641.0860797878. The cubic root of 21539680 is about 278.2358469913.

The spelling of 21539680 in words is "twenty-one million, five hundred thirty-nine thousand, six hundred eighty".