21538812 has 24 divisors (see below), whose sum is σ = 50464512. Its totient is φ = 7150000.

The previous prime is 21538789. The next prime is 21538841. The reversal of 21538812 is 21883512.

It is a self number, because there is not a number n which added to its sum of digits gives 21538812.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 564 + ... + 6587.

It is an arithmetic number, because the mean of its divisors is an integer number (2102688).

Almost surely, 2^21538812 is an apocalyptic number.

It is an amenable number.

21538812 is an abundant number, since it is smaller than the sum of its proper divisors (28925700).

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

21538812 is a wasteful number, since it uses less digits than its factorization.

21538812 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7409 (or 7407 counting only the distinct ones).

The product of its digits is 3840, while the sum is 30.

The square root of 21538812 is about 4640.9925662513. The cubic root of 21538812 is about 278.2321095177.

The spelling of 21538812 in words is "twenty-one million, five hundred thirty-eight thousand, eight hundred twelve".