99908991 has 96 divisors (see below), whose sum is σ = 191647680. Its totient is φ = 50948352.

The previous prime is 99908989. The next prime is 99909023. The reversal of 99908991 is 19980999.

It is not a de Polignac number, because 99908991 - 2¹ = 99908989 is a prime.

99908991 is a modest number, since divided by 8991 gives 999 as remainder.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99908791) by changing a digit.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 636285 + ... + 636441.

It is an arithmetic number, because the mean of its divisors is an integer number (1996330).

Almost surely, 2^99908991 is an apocalyptic number.

99908991 is a gapful number since it is divisible by the number (91) formed by its first and last digit.

99908991 is a deficient number, since it is larger than the sum of its proper divisors (91738689).

99908991 is a wasteful number, since it uses less digits than its factorization.

99908991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 230 (or 217 counting only the distinct ones).

The product of its (nonzero) digits is 472392, while the sum is 54.

The square root of 99908991 is about 9995.4485141989. The cubic root of 99908991 is about 464.0180318374.

It can be divided in two parts, 9990 and 8991, that added together give a palindrome (18981).

The spelling of 99908991 in words is "ninety-nine million, nine hundred eight thousand, nine hundred ninety-one".