3991997056815 has 32 divisors (see below), whose sum is σ = 7097344450560. Its totient is φ = 2128926858912.

The previous prime is 3991997056813. The next prime is 3991997056819. The reversal of 3991997056815 is 5186507991993.

3991997056815 is a `hidden beast` number, since 39 + 9 + 19 + 9 + 7 + 0 + 568 + 15 = 666.

3991997056815 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 3991997056815 - 2¹ = 3991997056813 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (3991997056813) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1143922 + ... + 3048368.

It is an arithmetic number, because the mean of its divisors is an integer number (221792014080).

Almost surely, 2^{3991997056815} is an apocalyptic number.

3991997056815 is a deficient number, since it is larger than the sum of its proper divisors (3105347393745).

3991997056815 is a wasteful number, since it uses less digits than its factorization.

3991997056815 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1919988 (or 1919982 counting only the distinct ones).

The product of its (nonzero) digits is 165337200, while the sum is 72.

The spelling of 3991997056815 in words is "three trillion, nine hundred ninety-one billion, nine hundred ninety-seven million, fifty-six thousand, eight hundred fifteen".