21279581831 has 4 divisors (see below), whose sum is σ = 21798596064. Its totient is φ = 20760567600.

The previous prime is 21279581737. The next prime is 21279581837. The reversal of 21279581831 is 13818597212.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21279581831 is a prime.

It is a super-2 number, since 2×21279581831² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21279581837) 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, 259507055 + ... + 259507136.

It is an arithmetic number, because the mean of its divisors is an integer number (5449649016).

Almost surely, 2^21279581831 is an apocalyptic number.

21279581831 is a deficient number, since it is larger than the sum of its proper divisors (519014233).

21279581831 is an equidigital number, since it uses as much as digits as its factorization.

21279581831 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 519014232.

The product of its digits is 241920, while the sum is 47.

The spelling of 21279581831 in words is "twenty-one billion, two hundred seventy-nine million, five hundred eighty-one thousand, eight hundred thirty-one".