79921409 has 2 divisors, whose sum is σ = 79921410. Its totient is φ = 79921408.

The previous prime is 79921399. The next prime is 79921411. The reversal of 79921409 is 90412997.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 73530625 + 6390784 = 8575^2 + 2528^2 .

It is a cyclic number.

It is not a de Polignac number, because 79921409 - 2⁴ = 79921393 is a prime.

It is a Sophie Germain prime.

Together with 79921411, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is not a weakly prime, because it can be changed into another prime (79921109) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39960704 + 39960705.

It is an arithmetic number, because the mean of its divisors is an integer number (39960705).

Almost surely, 2^79921409 is an apocalyptic number.

It is an amenable number.

79921409 is a deficient number, since it is larger than the sum of its proper divisors (1).

79921409 is an equidigital number, since it uses as much as digits as its factorization.

79921409 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 40824, while the sum is 41.

The square root of 79921409 is about 8939.8774600103. The cubic root of 79921409 is about 430.7457924625.

The spelling of 79921409 in words is "seventy-nine million, nine hundred twenty-one thousand, four hundred nine".