7991663 has 4 divisors (see below), whose sum is σ = 7997328. Its totient is φ = 7986000.

The previous prime is 7991657. The next prime is 7991701. The reversal of 7991663 is 3661997.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 3661997 = 41 ⋅89317.

It is a cyclic number.

It is not a de Polignac number, because 7991663 - 2⁸ = 7991407 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 7991663.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (7991623) 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, 1163 + ... + 4163.

It is an arithmetic number, because the mean of its divisors is an integer number (1999332).

Almost surely, 2^7991663 is an apocalyptic number.

7991663 is a deficient number, since it is larger than the sum of its proper divisors (5665).

7991663 is a wasteful number, since it uses less digits than its factorization.

7991663 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5664.

The product of its digits is 61236, while the sum is 41.

The square root of 7991663 is about 2826.9529532697. The cubic root of 7991663 is about 199.9305008521.

The spelling of 7991663 in words is "seven million, nine hundred ninety-one thousand, six hundred sixty-three".