99720991 has 8 divisors (see below), whose sum is σ = 102639744. Its totient is φ = 96844440.

The previous prime is 99720961. The next prime is 99721003. The reversal of 99720991 is 19902799.

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

It is a cyclic number.

It is not a de Polignac number, because 99720991 - 2¹⁵ = 99688223 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (99720961) 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, 5725 + ... + 15238.

It is an arithmetic number, because the mean of its divisors is an integer number (12829968).

Almost surely, 2^99720991 is an apocalyptic number.

99720991 is a deficient number, since it is larger than the sum of its proper divisors (2918753).

99720991 is a wasteful number, since it uses less digits than its factorization.

99720991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 21101.

The product of its (nonzero) digits is 91854, while the sum is 46.

The square root of 99720991 is about 9986.0398056487. The cubic root of 99720991 is about 463.7267995746.

The spelling of 99720991 in words is "ninety-nine million, seven hundred twenty thousand, nine hundred ninety-one".