7999991971 has 16 divisors (see below), whose sum is σ = 8984511360. Its totient is φ = 7078631040.

The previous prime is 7999991969. The next prime is 7999991981. The reversal of 7999991971 is 1791999997.

It is a cyclic number.

It is not a de Polignac number, because 7999991971 - 2¹ = 7999991969 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 7999991971.

It is not an unprimeable number, because it can be changed into a prime (7999991911) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 52221 + ... + 136846.

It is an arithmetic number, because the mean of its divisors is an integer number (561531960).

Almost surely, 2^7999991971 is an apocalyptic number.

7999991971 is a deficient number, since it is larger than the sum of its proper divisors (984519389).

7999991971 is a wasteful number, since it uses less digits than its factorization.

7999991971 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 189234.

The product of its digits is 26040609, while the sum is 70.

The square root of 7999991971 is about 89442.6742165058. The cubic root of 7999991971 is about 1999.9993309164. Note that the first 3 decimals are identical.

The spelling of 7999991971 in words is "seven billion, nine hundred ninety-nine million, nine hundred ninety-one thousand, nine hundred seventy-one".