991561850 has 12 divisors (see below), whose sum is σ = 1844305134. Its totient is φ = 396624720.

The previous prime is 991561849. The next prime is 991561859. The reversal of 991561850 is 58165199.

It can be written as a sum of positive squares in 3 ways, for example, as 957840601 + 33721249 = 30949^2 + 5807^2 .

It is not an unprimeable number, because it can be changed into a prime (991561859) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 9915569 + ... + 9915668.

Almost surely, 2^991561850 is an apocalyptic number.

991561850 is a deficient number, since it is larger than the sum of its proper divisors (852743284).

991561850 is a wasteful number, since it uses less digits than its factorization.

991561850 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 19831249 (or 19831244 counting only the distinct ones).

The product of its (nonzero) digits is 97200, while the sum is 44.

The square root of 991561850 is about 31489.0750896243. The cubic root of 991561850 is about 997.1793346609.

The spelling of 991561850 in words is "nine hundred ninety-one million, five hundred sixty-one thousand, eight hundred fifty".