691100991 has 48 divisors (see below), whose sum is σ = 1186884608. Its totient is φ = 393660000.

The previous prime is 691100989. The next prime is 691101049. The reversal of 691100991 is 199001196.

It is not a de Polignac number, because 691100991 - 2¹ = 691100989 is a prime.

It is a super-2 number, since 2×691100991² = 955241159522364162, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (691105991) 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 47 ways as a sum of consecutive naturals, for example, 919866 + ... + 920616.

Almost surely, 2^691100991 is an apocalyptic number.

691100991 is a deficient number, since it is larger than the sum of its proper divisors (495783617).

691100991 is an equidigital number, since it uses as much as digits as its factorization.

691100991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1314 (or 1302 counting only the distinct ones).

The product of its (nonzero) digits is 4374, while the sum is 36.

The square root of 691100991 is about 26288.7997253583. The cubic root of 691100991 is about 884.1253409593.

The spelling of 691100991 in words is "six hundred ninety-one million, one hundred thousand, nine hundred ninety-one".