7989991 has 4 divisors (see below), whose sum is σ = 8007712. Its totient is φ = 7972272.

The previous prime is 7989973. The next prime is 7990001. The reversal of 7989991 is 1999897.

7989991 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

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 7989991 - 2²¹ = 5892839 is a prime.

It is a Duffinian number.

7989991 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7989491) 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, 8166 + ... + 9091.

It is an arithmetic number, because the mean of its divisors is an integer number (2001928).

Almost surely, 2^7989991 is an apocalyptic number.

7989991 is a deficient number, since it is larger than the sum of its proper divisors (17721).

7989991 is a wasteful number, since it uses less digits than its factorization.

7989991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 17720.

The product of its digits is 367416, while the sum is 52.

The square root of 7989991 is about 2826.6572130345. The cubic root of 7989991 is about 199.9165568577.

The spelling of 7989991 in words is "seven million, nine hundred eighty-nine thousand, nine hundred ninety-one".