21538937 has 4 divisors (see below), whose sum is σ = 24615936. Its totient is φ = 18461940.

The previous prime is 21538903. The next prime is 21538939. The reversal of 21538937 is 73983512.

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 not a de Polignac number, because 21538937 - 2⁶ = 21538873 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21538937.

It is not an unprimeable number, because it can be changed into a prime (21538939) 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 3 ways as a sum of consecutive naturals, for example, 1538489 + ... + 1538502.

It is an arithmetic number, because the mean of its divisors is an integer number (6153984).

Almost surely, 2^21538937 is an apocalyptic number.

It is an amenable number.

21538937 is a deficient number, since it is larger than the sum of its proper divisors (3076999).

21538937 is an equidigital number, since it uses as much as digits as its factorization.

21538937 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3076998.

The product of its digits is 45360, while the sum is 38.

The square root of 21538937 is about 4641.0060331786. The cubic root of 21538937 is about 278.2326477545.

The spelling of 21538937 in words is "twenty-one million, five hundred thirty-eight thousand, nine hundred thirty-seven".