21918578279 has 4 divisors (see below), whose sum is σ = 23604622776. Its totient is φ = 20232533784.

The previous prime is 21918578273. The next prime is 21918578309. The reversal of 21918578279 is 97287581912.

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 21918578279 - 2²⁸ = 21650142823 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 (21918578273) 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, 843022229 + ... + 843022254.

It is an arithmetic number, because the mean of its divisors is an integer number (5901155694).

Almost surely, 2^21918578279 is an apocalyptic number.

21918578279 is a deficient number, since it is larger than the sum of its proper divisors (1686044497).

21918578279 is a wasteful number, since it uses less digits than its factorization.

21918578279 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1686044496.

The product of its digits is 5080320, while the sum is 59.

The spelling of 21918578279 in words is "twenty-one billion, nine hundred eighteen million, five hundred seventy-eight thousand, two hundred seventy-nine".