21123937 has 4 divisors (see below), whose sum is σ = 21413380. Its totient is φ = 20834496.

The previous prime is 21123917. The next prime is 21123983. The reversal of 21123937 is 73932112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 12967201 + 8156736 = 3601^2 + 2856^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21123937 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21123917) 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, 144612 + ... + 144757.

It is an arithmetic number, because the mean of its divisors is an integer number (5353345).

Almost surely, 2^21123937 is an apocalyptic number.

It is an amenable number.

21123937 is a deficient number, since it is larger than the sum of its proper divisors (289443).

21123937 is an equidigital number, since it uses as much as digits as its factorization.

21123937 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 289442.

The product of its digits is 2268, while the sum is 28.

The square root of 21123937 is about 4596.0784371027. The cubic root of 21123937 is about 276.4341038506.

The spelling of 21123937 in words is "twenty-one million, one hundred twenty-three thousand, nine hundred thirty-seven".