7999991 has 4 divisors (see below), whose sum is σ = 8009232. Its totient is φ = 7990752.

The previous prime is 7999963. The next prime is 7999993. The reversal of 7999991 is 1999997.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1999997 = 19 ⋅105263.

It is a cyclic number.

It is not a de Polignac number, because 7999991 - 2¹⁰ = 7998967 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 (7999993) 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, 3170 + ... + 5103.

It is an arithmetic number, because the mean of its divisors is an integer number (2002308).

Almost surely, 2^7999991 is an apocalyptic number.

7999991 is a deficient number, since it is larger than the sum of its proper divisors (9241).

7999991 is an equidigital number, since it uses as much as digits as its factorization.

7999991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9240.

The product of its digits is 413343, while the sum is 53.

The square root of 7999991 is about 2828.4255337555. The cubic root of 7999991 is about 199.9999250000. Note that the first 4 decimals are identical.

The spelling of 7999991 in words is "seven million, nine hundred ninety-nine thousand, nine hundred ninety-one".