991675561 has 4 divisors (see below), whose sum is σ = 1025871300. Its totient is φ = 957479824.

The previous prime is 991675549. The next prime is 991675571. The reversal of 991675561 is 165576199.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 165576199 = 9371 ⋅17669.

It can be written as a sum of positive squares in 2 ways, for example, as 833419161 + 158256400 = 28869^2 + 12580^2 .

It is a cyclic number.

It is not a de Polignac number, because 991675561 - 2²⁷ = 857457833 is a prime.

It is a Smith number, since the sum of its digits (49) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991675571) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 17097826 + ... + 17097883.

It is an arithmetic number, because the mean of its divisors is an integer number (256467825).

Almost surely, 2^991675561 is an apocalyptic number.

It is an amenable number.

991675561 is a deficient number, since it is larger than the sum of its proper divisors (34195739).

991675561 is a wasteful number, since it uses less digits than its factorization.

991675561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 34195738.

The product of its digits is 510300, while the sum is 49.

The square root of 991675561 is about 31490.8806005802. The cubic root of 991675561 is about 997.2174516058.

The spelling of 991675561 in words is "nine hundred ninety-one million, six hundred seventy-five thousand, five hundred sixty-one".