21578540 has 12 divisors (see below), whose sum is σ = 45314976. Its totient is φ = 8631408.

The previous prime is 21578539. The next prime is 21578563. The reversal of 21578540 is 4587512.

It is a junction number, because it is equal to n+sod(n) for n = 21578497 and 21578506.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 539444 + ... + 539483.

It is an arithmetic number, because the mean of its divisors is an integer number (3776248).

Almost surely, 2^21578540 is an apocalyptic number.

21578540 is a gapful number since it is divisible by the number (20) formed by its first and last digit.

It is an amenable number.

21578540 is an abundant number, since it is smaller than the sum of its proper divisors (23736436).

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

21578540 is a wasteful number, since it uses less digits than its factorization.

21578540 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1078936 (or 1078934 counting only the distinct ones).

The product of its (nonzero) digits is 11200, while the sum is 32.

The square root of 21578540 is about 4645.2707133169. The cubic root of 21578540 is about 278.4030693666.

The spelling of 21578540 in words is "twenty-one million, five hundred seventy-eight thousand, five hundred forty".