21865457 has 4 divisors (see below), whose sum is σ = 22374000. Its totient is φ = 21356916.

The previous prime is 21865439. The next prime is 21865469. The reversal of 21865457 is 75456812.

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 21865457 - 2¹⁸ = 21603313 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 21865457.

It is not an unprimeable number, because it can be changed into a prime (21865427) 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, 254207 + ... + 254292.

It is an arithmetic number, because the mean of its divisors is an integer number (5593500).

Almost surely, 2^21865457 is an apocalyptic number.

It is an amenable number.

21865457 is a deficient number, since it is larger than the sum of its proper divisors (508543).

21865457 is an equidigital number, since it uses as much as digits as its factorization.

21865457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 508542.

The product of its digits is 67200, while the sum is 38.

The square root of 21865457 is about 4676.0514325657. The cubic root of 21865457 is about 279.6315604675.

It can be divided in two parts, 21865 and 457, that added together give a palindrome (22322).

The spelling of 21865457 in words is "twenty-one million, eight hundred sixty-five thousand, four hundred fifty-seven".