21805457 has 4 divisors (see below), whose sum is σ = 21950016. Its totient is φ = 21660900.

The previous prime is 21805451. The next prime is 21805463. The reversal of 21805457 is 75450812.

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 an interprime number because it is at equal distance from previous prime (21805451) and next prime (21805463).

It is a cyclic number.

It is not a de Polignac number, because 21805457 - 2²⁴ = 5028241 is a prime.

It is a super-3 number, since 3×21805457³ (a number of 23 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21805451) 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, 72053 + ... + 72354.

It is an arithmetic number, because the mean of its divisors is an integer number (5487504).

Almost surely, 2^21805457 is an apocalyptic number.

It is an amenable number.

21805457 is a deficient number, since it is larger than the sum of its proper divisors (144559).

21805457 is a wasteful number, since it uses less digits than its factorization.

21805457 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 144558.

The product of its (nonzero) digits is 11200, while the sum is 32.

The square root of 21805457 is about 4669.6313558995. The cubic root of 21805457 is about 279.3755514339.

The spelling of 21805457 in words is "twenty-one million, eight hundred five thousand, four hundred fifty-seven".