991917565801 has 32 divisors (see below), whose sum is σ = 1065699968256. Its totient is φ = 920937600000.

The previous prime is 991917565777. The next prime is 991917565843. The reversal of 991917565801 is 108565719199.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-991917565801 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 991917565801.

It is not an unprimeable number, because it can be changed into a prime (991917565201) 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, 173987251 + ... + 173992951.

It is an arithmetic number, because the mean of its divisors is an integer number (33303124008).

Almost surely, 2^991917565801 is an apocalyptic number.

It is an amenable number.

991917565801 is a deficient number, since it is larger than the sum of its proper divisors (73782402455).

991917565801 is a wasteful number, since it uses less digits than its factorization.

991917565801 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6673.

The product of its (nonzero) digits is 6123600, while the sum is 61.

The spelling of 991917565801 in words is "nine hundred ninety-one billion, nine hundred seventeen million, five hundred sixty-five thousand, eight hundred one".