991309977 has 24 divisors (see below), whose sum is σ = 1638434304. Its totient is φ = 565775424.

The previous prime is 991309973. The next prime is 991309981. The reversal of 991309977 is 779903199.

It is an interprime number because it is at equal distance from previous prime (991309973) and next prime (991309981).

It is not a de Polignac number, because 991309977 - 2² = 991309973 is a prime.

It is not an unprimeable number, because it can be changed into a prime (991309973) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 45253 + ... + 63485.

It is an arithmetic number, because the mean of its divisors is an integer number (68268096).

Almost surely, 2^991309977 is an apocalyptic number.

It is an amenable number.

991309977 is a deficient number, since it is larger than the sum of its proper divisors (647124327).

991309977 is a wasteful number, since it uses less digits than its factorization.

991309977 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19109 (or 19106 counting only the distinct ones).

The product of its (nonzero) digits is 964467, while the sum is 54.

The square root of 991309977 is about 31485.0754644165. The cubic root of 991309977 is about 997.0948941996.

The spelling of 991309977 in words is "nine hundred ninety-one million, three hundred nine thousand, nine hundred seventy-seven".