91997731776 has 28 divisors (see below), whose sum is σ = 243410665832. Its totient is φ = 30665910528.

The previous prime is 91997731769. The next prime is 91997731783. The reversal of 91997731776 is 67713779919.

It is an interprime number because it is at equal distance from previous prime (91997731769) and next prime (91997731783).

It is a super-2 number, since 2×91997731776² (a number of 23 digits) contains 22 as substring.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 239577235 + ... + 239577618.

Almost surely, 2^91997731776 is an apocalyptic number.

91997731776 is a gapful number since it is divisible by the number (96) formed by its first and last digit.

It is an amenable number.

91997731776 is an abundant number, since it is smaller than the sum of its proper divisors (151412934056).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

91997731776 is a wasteful number, since it uses less digits than its factorization.

91997731776 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 479154868 (or 479154858 counting only the distinct ones).

The product of its digits is 31505922, while the sum is 66.

The spelling of 91997731776 in words is "ninety-one billion, nine hundred ninety-seven million, seven hundred thirty-one thousand, seven hundred seventy-six".