7991881 has 4 divisors (see below), whose sum is σ = 8010772. Its totient is φ = 7972992.

The previous prime is 7991869. The next prime is 7991891. The reversal of 7991881 is 1881997.

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

It can be written as a sum of positive squares in 2 ways, for example, as 3222025 + 4769856 = 1795^2 + 2184^2 .

It is a cyclic number.

It is not a de Polignac number, because 7991881 - 2⁹ = 7991369 is a prime.

It is a super-2 number, since 2×7991881² = 127740323836322, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7991891) 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 in 3 ways as a sum of consecutive naturals, for example, 8796 + ... + 9661.

It is an arithmetic number, because the mean of its divisors is an integer number (2002693).

Almost surely, 2^7991881 is an apocalyptic number.

It is an amenable number.

7991881 is a deficient number, since it is larger than the sum of its proper divisors (18891).

7991881 is a wasteful number, since it uses less digits than its factorization.

7991881 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18890.

The product of its digits is 36288, while the sum is 43.

The square root of 7991881 is about 2826.9915104223. The cubic root of 7991881 is about 199.9323187655.

The spelling of 7991881 in words is "seven million, nine hundred ninety-one thousand, eight hundred eighty-one".