3991159981 has 2 divisors, whose sum is σ = 3991159982. Its totient is φ = 3991159980.

The previous prime is 3991159979. The next prime is 3991159987. The reversal of 3991159981 is 1899511993.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 2037077956 + 1954082025 = 45134^2 + 44205^2 .

It is a cyclic number.

It is not a de Polignac number, because 3991159981 - 2¹ = 3991159979 is a prime.

It is a super-2 number, since 2×3991159981² = 31858715987871840722, which contains 22 as substring.

Together with 3991159979, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (3991159987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1995579990 + 1995579991.

It is an arithmetic number, because the mean of its divisors is an integer number (1995579991).

Almost surely, 2^3991159981 is an apocalyptic number.

It is an amenable number.

3991159981 is a deficient number, since it is larger than the sum of its proper divisors (1).

3991159981 is an equidigital number, since it uses as much as digits as its factorization.

3991159981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 787320, while the sum is 55.

The square root of 3991159981 is about 63175.6280617771. The cubic root of 3991159981 is about 1586.2308015030.

The spelling of 3991159981 in words is "three billion, nine hundred ninety-one million, one hundred fifty-nine thousand, nine hundred eighty-one".