21366957 has 4 divisors (see below), whose sum is σ = 28489280. Its totient is φ = 14244636.

The previous prime is 21366913. The next prime is 21366971. The reversal of 21366957 is 75966312.

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 21366957 - 2¹⁰ = 21365933 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21366907) 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, 3561157 + ... + 3561162.

It is an arithmetic number, because the mean of its divisors is an integer number (7122320).

Almost surely, 2^21366957 is an apocalyptic number.

It is an amenable number.

21366957 is a deficient number, since it is larger than the sum of its proper divisors (7122323).

21366957 is an equidigital number, since it uses as much as digits as its factorization.

21366957 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7122322.

The product of its digits is 68040, while the sum is 39.

The square root of 21366957 is about 4622.4405891261. The cubic root of 21366957 is about 277.4901416837.

The spelling of 21366957 in words is "twenty-one million, three hundred sixty-six thousand, nine hundred fifty-seven".