21365457 has 4 divisors (see below), whose sum is σ = 28487280. Its totient is φ = 14243636.

The previous prime is 21365441. The next prime is 21365497. The reversal of 21365457 is 75456312.

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 not a de Polignac number, because 21365457 - 2⁴ = 21365441 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21365497) 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, 3560907 + ... + 3560912.

It is an arithmetic number, because the mean of its divisors is an integer number (7121820).

Almost surely, 2^21365457 is an apocalyptic number.

It is an amenable number.

21365457 is a deficient number, since it is larger than the sum of its proper divisors (7121823).

21365457 is an equidigital number, since it uses as much as digits as its factorization.

21365457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7121822.

The product of its digits is 25200, while the sum is 33.

The square root of 21365457 is about 4622.2783343282. The cubic root of 21365457 is about 277.4836480909.

The spelling of 21365457 in words is "twenty-one million, three hundred sixty-five thousand, four hundred fifty-seven".