21538837 has 4 divisors (see below), whose sum is σ = 22672480. Its totient is φ = 20405196.

The previous prime is 21538789. The next prime is 21538841. The reversal of 21538837 is 73883512.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21538837 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21538796 and 21538805.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21538897) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 566793 + ... + 566830.

It is an arithmetic number, because the mean of its divisors is an integer number (5668120).

Almost surely, 2^21538837 is an apocalyptic number.

It is an amenable number.

21538837 is a deficient number, since it is larger than the sum of its proper divisors (1133643).

21538837 is a wasteful number, since it uses less digits than its factorization.

21538837 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1133642.

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

The square root of 21538837 is about 4640.9952596399. The cubic root of 21538837 is about 278.2322171652.

The spelling of 21538837 in words is "twenty-one million, five hundred thirty-eight thousand, eight hundred thirty-seven".