991987566967 has 16 divisors (see below), whose sum is σ = 1000668654720. Its totient is φ = 983343160800.

The previous prime is 991987566949. The next prime is 991987566989. The reversal of 991987566967 is 769665789199.

It is a cyclic number.

It is not a de Polignac number, because 991987566967 - 2⁷ = 991987566839 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 (991987566667) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 197959492 + ... + 197964502.

It is an arithmetic number, because the mean of its divisors is an integer number (62541790920).

Almost surely, 2^991987566967 is an apocalyptic number.

991987566967 is a deficient number, since it is larger than the sum of its proper divisors (8681087753).

991987566967 is a wasteful number, since it uses less digits than its factorization.

991987566967 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 8334.

The product of its digits is 2777664960, while the sum is 82.

The spelling of 991987566967 in words is "nine hundred ninety-one billion, nine hundred eighty-seven million, five hundred sixty-six thousand, nine hundred sixty-seven".