99910991 has 4 divisors (see below), whose sum is σ = 99930984. Its totient is φ = 99891000.

The previous prime is 99910963. The next prime is 99910997. The reversal of 99910991 is 19901999.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 99910991 - 2¹⁴ = 99894607 is a prime.

It is a super-2 number, since 2×99910991² = 19964412245204162, 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 (99910997) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 4856 + ... + 14946.

It is an arithmetic number, because the mean of its divisors is an integer number (24982746).

Almost surely, 2^99910991 is an apocalyptic number.

99910991 is a deficient number, since it is larger than the sum of its proper divisors (19993).

99910991 is a wasteful number, since it uses less digits than its factorization.

99910991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19992.

The product of its (nonzero) digits is 59049, while the sum is 47.

The square root of 99910991 is about 9995.5485592338. The cubic root of 99910991 is about 464.0211280882.

It can be divided in two parts, 99 and 910991, that multiplied together give a palindrome (90188109).

The spelling of 99910991 in words is "ninety-nine million, nine hundred ten thousand, nine hundred ninety-one".