991591247 has 4 divisors (see below), whose sum is σ = 1043780280. Its totient is φ = 939402216.

The previous prime is 991591243. The next prime is 991591253. The reversal of 991591247 is 742195199.

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 991591247 - 2² = 991591243 is a prime.

It is a super-2 number, since 2×991591247² = 1966506402254030018, 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 (991591243) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 26094488 + ... + 26094525.

It is an arithmetic number, because the mean of its divisors is an integer number (260945070).

Almost surely, 2^991591247 is an apocalyptic number.

991591247 is a deficient number, since it is larger than the sum of its proper divisors (52189033).

991591247 is a wasteful number, since it uses less digits than its factorization.

991591247 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 52189032.

The product of its digits is 204120, while the sum is 47.

The square root of 991591247 is about 31489.5418671025. The cubic root of 991591247 is about 997.1891890777.

The spelling of 991591247 in words is "nine hundred ninety-one million, five hundred ninety-one thousand, two hundred forty-seven".