991951099 has 4 divisors (see below), whose sum is σ = 997090936. Its totient is φ = 986811264.

The previous prime is 991951043. The next prime is 991951117. The reversal of 991951099 is 990159199.

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 991951099 - 2¹⁹ = 991426811 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991951039) 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, 2569629 + ... + 2570014.

It is an arithmetic number, because the mean of its divisors is an integer number (249272734).

Almost surely, 2^991951099 is an apocalyptic number.

991951099 is a deficient number, since it is larger than the sum of its proper divisors (5139837).

991951099 is a wasteful number, since it uses less digits than its factorization.

991951099 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5139836.

The product of its (nonzero) digits is 295245, while the sum is 52.

The square root of 991951099 is about 31495.2551823287. The cubic root of 991951099 is about 997.3098023263.

The spelling of 991951099 in words is "nine hundred ninety-one million, nine hundred fifty-one thousand, ninety-nine".