21538385 has 16 divisors (see below), whose sum is σ = 28321920. Its totient is φ = 15594240.

The previous prime is 21538379. The next prime is 21538393. The reversal of 21538385 is 58383512.

It is not a de Polignac number, because 21538385 - 2¹⁴ = 21522001 is a prime.

It is a Curzon number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13721 + ... + 15209.

It is an arithmetic number, because the mean of its divisors is an integer number (1770120).

Almost surely, 2^21538385 is an apocalyptic number.

It is an amenable number.

21538385 is a deficient number, since it is larger than the sum of its proper divisors (6783535).

21538385 is a wasteful number, since it uses less digits than its factorization.

21538385 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1768.

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

The square root of 21538385 is about 4640.9465629330. The cubic root of 21538385 is about 278.2302708849.

The spelling of 21538385 in words is "twenty-one million, five hundred thirty-eight thousand, three hundred eighty-five".