21279749 has 2 divisors, whose sum is σ = 21279750. Its totient is φ = 21279748.

The previous prime is 21279737. The next prime is 21279757. The reversal of 21279749 is 94797212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11607649 + 9672100 = 3407^2 + 3110^2 .

It is a cyclic number.

It is not a de Polignac number, because 21279749 - 2⁸ = 21279493 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21279949) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10639874 + 10639875.

It is an arithmetic number, because the mean of its divisors is an integer number (10639875).

Almost surely, 2^21279749 is an apocalyptic number.

It is an amenable number.

21279749 is a deficient number, since it is larger than the sum of its proper divisors (1).

21279749 is an equidigital number, since it uses as much as digits as its factorization.

21279749 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 63504, while the sum is 41.

The square root of 21279749 is about 4612.9978322128. The cubic root of 21279749 is about 277.1121069158.

The spelling of 21279749 in words is "twenty-one million, two hundred seventy-nine thousand, seven hundred forty-nine".