99991231 has 16 divisors (see below), whose sum is σ = 105162624. Its totient is φ = 94991104.

The previous prime is 99991207. The next prime is 99991237. The reversal of 99991231 is 13219999.

It is a cyclic number.

It is not a de Polignac number, because 99991231 - 2⁷ = 99991103 is a prime.

It is a super-2 number, since 2×99991231² = 19996492553790722, which 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 (99991237) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 341121 + ... + 341413.

It is an arithmetic number, because the mean of its divisors is an integer number (6572664).

Almost surely, 2^99991231 is an apocalyptic number.

99991231 is a deficient number, since it is larger than the sum of its proper divisors (5171393).

99991231 is a wasteful number, since it uses less digits than its factorization.

99991231 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 530.

The product of its digits is 39366, while the sum is 43.

The square root of 99991231 is about 9999.5615403877. The cubic root of 99991231 is about 464.1453156005.

The spelling of 99991231 in words is "ninety-nine million, nine hundred ninety-one thousand, two hundred thirty-one".