21457905793 has 4 divisors (see below), whose sum is σ = 21459396420. Its totient is φ = 21456415168.

The previous prime is 21457905757. The next prime is 21457905803. The reversal of 21457905793 is 39750975412.

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 12019394689 + 9438511104 = 109633^2 + 97152^2 .

It is a cyclic number.

It is not a de Polignac number, because 21457905793 - 2²¹ = 21455808641 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 21457905793.

It is not an unprimeable number, because it can be changed into a prime (21457005793) 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, 723508 + ... + 752581.

It is an arithmetic number, because the mean of its divisors is an integer number (5364849105).

Almost surely, 2^21457905793 is an apocalyptic number.

It is an amenable number.

21457905793 is a deficient number, since it is larger than the sum of its proper divisors (1490627).

21457905793 is a wasteful number, since it uses less digits than its factorization.

21457905793 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1490626.

The product of its (nonzero) digits is 2381400, while the sum is 52.

The spelling of 21457905793 in words is "twenty-one billion, four hundred fifty-seven million, nine hundred five thousand, seven hundred ninety-three".