991813491 has 24 divisors (see below), whose sum is σ = 1491300720. Its totient is φ = 658707552.

The previous prime is 991813409. The next prime is 991813513. The reversal of 991813491 is 194318199.

It is not a de Polignac number, because 991813491 - 2¹⁰ = 991812467 is a prime.

It is not an unprimeable number, because it can be changed into a prime (991813391) 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, 57781 + ... + 72953.

It is an arithmetic number, because the mean of its divisors is an integer number (62137530).

Almost surely, 2^991813491 is an apocalyptic number.

991813491 is a deficient number, since it is larger than the sum of its proper divisors (499487229).

991813491 is a wasteful number, since it uses less digits than its factorization.

991813491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15457 (or 15445 counting only the distinct ones).

The product of its digits is 69984, while the sum is 45.

The square root of 991813491 is about 31493.0705235295. The cubic root of 991813491 is about 997.2636830656.

It can be divided in two parts, 9918 and 13491, that added together give a square (23409 = 153²).

The spelling of 991813491 in words is "nine hundred ninety-one million, eight hundred thirteen thousand, four hundred ninety-one".