21538538 has 24 divisors (see below), whose sum is σ = 37767744. Its totient is φ = 9185400.

The previous prime is 21538523. The next prime is 21538547. The reversal of 21538538 is 83583512.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 21538498 and 21538507.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 26153 + ... + 26963.

It is an arithmetic number, because the mean of its divisors is an integer number (1573656).

Almost surely, 2^21538538 is an apocalyptic number.

21538538 is a deficient number, since it is larger than the sum of its proper divisors (16229206).

21538538 is a wasteful number, since it uses less digits than its factorization.

21538538 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1098 (or 1091 counting only the distinct ones).

The product of its digits is 28800, while the sum is 35.

The square root of 21538538 is about 4640.9630466100. The cubic root of 21538538 is about 278.2309296952.

The spelling of 21538538 in words is "twenty-one million, five hundred thirty-eight thousand, five hundred thirty-eight".