79999991 has 4 divisors (see below), whose sum is σ = 80196000. Its totient is φ = 79803984.

The previous prime is 79999987. The next prime is 80000023. The reversal of 79999991 is 19999997.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 79999991 - 2² = 79999987 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (79999981) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 97391 + ... + 98208.

It is an arithmetic number, because the mean of its divisors is an integer number (20049000).

Almost surely, 2^79999991 is an apocalyptic number.

79999991 is a deficient number, since it is larger than the sum of its proper divisors (196009).

79999991 is a wasteful number, since it uses less digits than its factorization.

79999991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 196008.

The product of its digits is 3720087, while the sum is 62.

The square root of 79999991 is about 8944.2714068838. The cubic root of 79999991 is about 430.8869218481.

It can be divided in two parts, 7999999 and 1, that added together give a cube (8000000 = 200³).

The spelling of 79999991 in words is "seventy-nine million, nine hundred ninety-nine thousand, nine hundred ninety-one".