21279737 has 2 divisors, whose sum is σ = 21279738. Its totient is φ = 21279736.

The previous prime is 21279721. The next prime is 21279749. The reversal of 21279737 is 73797212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20394256 + 885481 = 4516^2 + 941^2 .

It is a cyclic number.

It is not a de Polignac number, because 21279737 - 2⁴ = 21279721 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21279737.

It is not a weakly prime, because it can be changed into another prime (21279757) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10639868 + 10639869.

It is an arithmetic number, because the mean of its divisors is an integer number (10639869).

Almost surely, 2^21279737 is an apocalyptic number.

It is an amenable number.

21279737 is a deficient number, since it is larger than the sum of its proper divisors (1).

21279737 is an equidigital number, since it uses as much as digits as its factorization.

21279737 is an evil number, because the sum of its binary digits is even.

The product of its digits is 37044, while the sum is 38.

The square root of 21279737 is about 4612.9965315400. The cubic root of 21279737 is about 277.1120548264.

The spelling of 21279737 in words is "twenty-one million, two hundred seventy-nine thousand, seven hundred thirty-seven".