991640168972 has 12 divisors (see below), whose sum is σ = 1735378254120. Its totient is φ = 495817810656.

The previous prime is 991640168929. The next prime is 991640168977. The reversal of 991640168972 is 279861046199.

It is not an unprimeable number, because it can be changed into a prime (991640168977) 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, 755303 + ... + 1598049.

It is an arithmetic number, because the mean of its divisors is an integer number (144614854510).

Almost surely, 2^991640168972 is an apocalyptic number.

It is an amenable number.

991640168972 is a deficient number, since it is larger than the sum of its proper divisors (743738085148).

991640168972 is a wasteful number, since it uses less digits than its factorization.

991640168972 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1136920 (or 1136918 counting only the distinct ones).

The product of its (nonzero) digits is 11757312, while the sum is 62.

The spelling of 991640168972 in words is "nine hundred ninety-one billion, six hundred forty million, one hundred sixty-eight thousand, nine hundred seventy-two".