991697305599 has 128 divisors (see below), whose sum is σ = 1976750899200. Its totient is φ = 474540197760.

The previous prime is 991697305541. The next prime is 991697305603. The reversal of 991697305599 is 995503796199.

991697305599 is a `hidden beast` number, since 9 + 9 + 1 + 69 + 7 + 3 + 0 + 559 + 9 = 666.

It is a Cunningham number, because it is equal to 995840²-1.

It is not a de Polignac number, because 991697305599 - 2¹⁶ = 991697240063 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991697315599) by changing a digit.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 12907632 + ... + 12984234.

It is an arithmetic number, because the mean of its divisors is an integer number (15443366400).

Almost surely, 2^991697305599 is an apocalyptic number.

991697305599 is a gapful number since it is divisible by the number (99) formed by its first and last digit.

991697305599 is a deficient number, since it is larger than the sum of its proper divisors (985053593601).

991697305599 is a wasteful number, since it uses less digits than its factorization.

991697305599 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 77122 (or 77116 counting only the distinct ones).

The product of its (nonzero) digits is 186004350, while the sum is 72.

The spelling of 991697305599 in words is "nine hundred ninety-one billion, six hundred ninety-seven million, three hundred five thousand, five hundred ninety-nine".