8199991 has 4 divisors (see below), whose sum is σ = 8242672. Its totient is φ = 8157312.

The previous prime is 8199979. The next prime is 8200007. The reversal of 8199991 is 1999918.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1999918 = 2 ⋅999959.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-8199991 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 (8199901) 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, 21051 + ... + 21436.

It is an arithmetic number, because the mean of its divisors is an integer number (2060668).

Almost surely, 2^8199991 is an apocalyptic number.

8199991 is a deficient number, since it is larger than the sum of its proper divisors (42681).

8199991 is a wasteful number, since it uses less digits than its factorization.

8199991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 42680.

The product of its digits is 52488, while the sum is 46.

The square root of 8199991 is about 2863.5626411867. The cubic root of 8199991 is about 201.6528937463.

The spelling of 8199991 in words is "eight million, one hundred ninety-nine thousand, nine hundred ninety-one".