21637649479 has 4 divisors (see below), whose sum is σ = 21638013976. Its totient is φ = 21637284984.

The previous prime is 21637649471. The next prime is 21637649497. The reversal of 21637649479 is 97494673612.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21637649479 - 2³ = 21637649471 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 (21637649471) 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, 70269 + ... + 219574.

It is an arithmetic number, because the mean of its divisors is an integer number (5409503494).

Almost surely, 2^21637649479 is an apocalyptic number.

21637649479 is a deficient number, since it is larger than the sum of its proper divisors (364497).

21637649479 is an equidigital number, since it uses as much as digits as its factorization.

21637649479 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 364496.

The product of its digits is 13716864, while the sum is 58.

The spelling of 21637649479 in words is "twenty-one billion, six hundred thirty-seven million, six hundred forty-nine thousand, four hundred seventy-nine".