21537637361 has 4 divisors (see below), whose sum is σ = 21598650852. Its totient is φ = 21476623872.

The previous prime is 21537637357. The next prime is 21537637367. The reversal of 21537637361 is 16373673512.

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 14557870336 + 6979767025 = 120656^2 + 83545^2 .

It is a cyclic number.

It is not a de Polignac number, because 21537637361 - 2² = 21537637357 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21537637367) 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, 30506216 + ... + 30506921.

It is an arithmetic number, because the mean of its divisors is an integer number (5399662713).

Almost surely, 2^21537637361 is an apocalyptic number.

It is an amenable number.

21537637361 is a deficient number, since it is larger than the sum of its proper divisors (61013491).

21537637361 is an equidigital number, since it uses as much as digits as its factorization.

21537637361 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 61013490.

The product of its digits is 476280, while the sum is 44.

The spelling of 21537637361 in words is "twenty-one billion, five hundred thirty-seven million, six hundred thirty-seven thousand, three hundred sixty-one".