21538387 has 8 divisors (see below), whose sum is σ = 23995440. Its totient is φ = 19195680.

The previous prime is 21538379. The next prime is 21538393. The reversal of 21538387 is 78383512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21538387 - 2³ = 21538379 is a prime.

It is a super-2 number, since 2×21538387² = 927804229123538, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21538487) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 28189 + ... + 28942.

It is an arithmetic number, because the mean of its divisors is an integer number (2999430).

Almost surely, 2^21538387 is an apocalyptic number.

21538387 is a deficient number, since it is larger than the sum of its proper divisors (2457053).

21538387 is a wasteful number, since it uses less digits than its factorization.

21538387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 57173.

The product of its digits is 40320, while the sum is 37.

The square root of 21538387 is about 4640.9467784063. The cubic root of 21538387 is about 278.2302794968.

The spelling of 21538387 in words is "twenty-one million, five hundred thirty-eight thousand, three hundred eighty-seven".