991705571 has 12 divisors (see below), whose sum is σ = 1012669344. Its totient is φ = 971163600.

The previous prime is 991705553. The next prime is 991705573. The reversal of 991705571 is 175507199.

It is not a de Polignac number, because 991705571 - 2¹⁴ = 991689187 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991705573) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1499981 + ... + 1500641.

It is an arithmetic number, because the mean of its divisors is an integer number (84389112).

Almost surely, 2^991705571 is an apocalyptic number.

991705571 is a deficient number, since it is larger than the sum of its proper divisors (20963773).

991705571 is an equidigital number, since it uses as much as digits as its factorization.

991705571 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1210 (or 1151 counting only the distinct ones).

The product of its (nonzero) digits is 99225, while the sum is 44.

The square root of 991705571 is about 31491.3570841271. The cubic root of 991705571 is about 997.2275107404.

The spelling of 991705571 in words is "nine hundred ninety-one million, seven hundred five thousand, five hundred seventy-one".