21278365631 has 12 divisors (see below), whose sum is σ = 21880347048. Its totient is φ = 20692534752.

The previous prime is 21278365597. The next prime is 21278365643. The reversal of 21278365631 is 13656387212.

It is a de Polignac number, because none of the positive numbers 2^k-21278365631 is a prime.

It is a super-2 number, since 2×21278365631² (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 (21278365651) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 4360565 + ... + 4365441.

It is an arithmetic number, because the mean of its divisors is an integer number (1823362254).

Almost surely, 2^21278365631 is an apocalyptic number.

21278365631 is a deficient number, since it is larger than the sum of its proper divisors (601981417).

21278365631 is an equidigital number, since it uses as much as digits as its factorization.

21278365631 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8138 (or 8101 counting only the distinct ones).

The product of its digits is 362880, while the sum is 44.

The spelling of 21278365631 in words is "twenty-one billion, two hundred seventy-eight million, three hundred sixty-five thousand, six hundred thirty-one".