21253738357 has 4 divisors (see below), whose sum is σ = 21828163756. Its totient is φ = 20679312960.

The previous prime is 21253738309. The next prime is 21253738369. The reversal of 21253738357 is 75383735212.

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 12085484356 + 9168254001 = 109934^2 + 95751^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21253738357 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 (21253738397) 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, 287212644 + ... + 287212717.

It is an arithmetic number, because the mean of its divisors is an integer number (5457040939).

Almost surely, 2^21253738357 is an apocalyptic number.

It is an amenable number.

21253738357 is a deficient number, since it is larger than the sum of its proper divisors (574425399).

21253738357 is an equidigital number, since it uses as much as digits as its factorization.

21253738357 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 574425398.

The product of its digits is 1058400, while the sum is 46.

The spelling of 21253738357 in words is "twenty-one billion, two hundred fifty-three million, seven hundred thirty-eight thousand, three hundred fifty-seven".