991497026631 has 8 divisors (see below), whose sum is σ = 1327768944880. Its totient is φ = 658111563072.

The previous prime is 991497026623. The next prime is 991497026677. The reversal of 991497026631 is 136620794199.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 991497026631 - 2³ = 991497026623 is a prime.

It is a super-2 number, since 2×991497026631² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991497026621) 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, 721612870 + ... + 721614243.

It is an arithmetic number, because the mean of its divisors is an integer number (165971118110).

Almost surely, 2^991497026631 is an apocalyptic number.

991497026631 is a deficient number, since it is larger than the sum of its proper divisors (336271918249).

991497026631 is a wasteful number, since it uses less digits than its factorization.

991497026631 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1443227345.

The product of its (nonzero) digits is 4408992, while the sum is 57.

The spelling of 991497026631 in words is "nine hundred ninety-one billion, four hundred ninety-seven million, twenty-six thousand, six hundred thirty-one".