3991856618 has 4 divisors (see below), whose sum is σ = 5987784930. Its totient is φ = 1995928308.

The previous prime is 3991856587. The next prime is 3991856621. The reversal of 3991856618 is 8166581993.

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

It can be written as a sum of positive squares in only one way, i.e., 3618864649 + 372991969 = 60157^2 + 19313^2 .

It is an unprimeable number.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 997964153 + ... + 997964156.

Almost surely, 2^3991856618 is an apocalyptic number.

3991856618 is a deficient number, since it is larger than the sum of its proper divisors (1995928312).

3991856618 is a wasteful number, since it uses less digits than its factorization.

3991856618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1995928311.

The product of its digits is 2799360, while the sum is 56.

The square root of 3991856618 is about 63181.1413160604. The cubic root of 3991856618 is about 1586.3230856832.

The spelling of 3991856618 in words is "three billion, nine hundred ninety-one million, eight hundred fifty-six thousand, six hundred eighteen".