991731013688 has 32 divisors (see below), whose sum is σ = 1902336105600. Its totient is φ = 484542040032.

The previous prime is 991731013681. The next prime is 991731013711. The reversal of 991731013688 is 886310137199.

It is a super-2 number, since 2×991731013688² (a number of 25 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991731013681) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6211970 + ... + 6369617.

It is an arithmetic number, because the mean of its divisors is an integer number (59448003300).

Almost surely, 2^991731013688 is an apocalyptic number.

It is an amenable number.

991731013688 is a deficient number, since it is larger than the sum of its proper divisors (910605091912).

991731013688 is a wasteful number, since it uses less digits than its factorization.

991731013688 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 12581819 (or 12581815 counting only the distinct ones).

The product of its (nonzero) digits is 1959552, while the sum is 56.

The spelling of 991731013688 in words is "nine hundred ninety-one billion, seven hundred thirty-one million, thirteen thousand, six hundred eighty-eight".