79721591 has 2 divisors, whose sum is σ = 79721592. Its totient is φ = 79721590.

The previous prime is 79721573. The next prime is 79721597. The reversal of 79721591 is 19512797.

It is a happy number.

It is a strong prime.

It is an emirp because it is prime and its reverse (19512797) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 79721591 - 2¹⁸ = 79459447 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (79721597) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 39860795 + 39860796.

It is an arithmetic number, because the mean of its divisors is an integer number (39860796).

Almost surely, 2^79721591 is an apocalyptic number.

79721591 is a deficient number, since it is larger than the sum of its proper divisors (1).

79721591 is an equidigital number, since it uses as much as digits as its factorization.

79721591 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 39690, while the sum is 41.

The square root of 79721591 is about 8928.6948094332. The cubic root of 79721591 is about 430.3865120374.

The spelling of 79721591 in words is "seventy-nine million, seven hundred twenty-one thousand, five hundred ninety-one".