21279431 has 2 divisors, whose sum is σ = 21279432. Its totient is φ = 21279430.

The previous prime is 21279421. The next prime is 21279443. The reversal of 21279431 is 13497212.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21279431 is a prime.

It is a super-2 number, since 2×21279431² = 905628367367522, which contains 22 as substring.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 21279394 and 21279403.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21279421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10639715 + 10639716.

It is an arithmetic number, because the mean of its divisors is an integer number (10639716).

Almost surely, 2^21279431 is an apocalyptic number.

21279431 is a deficient number, since it is larger than the sum of its proper divisors (1).

21279431 is an equidigital number, since it uses as much as digits as its factorization.

21279431 is an evil number, because the sum of its binary digits is even.

The product of its digits is 3024, while the sum is 29.

The square root of 21279431 is about 4612.9633642595. The cubic root of 21279431 is about 277.1107265409.

The spelling of 21279431 in words is "twenty-one million, two hundred seventy-nine thousand, four hundred thirty-one".