991276561 has 4 divisors (see below), whose sum is σ = 1081392624. Its totient is φ = 901160500.

The previous prime is 991276541. The next prime is 991276603. The reversal of 991276561 is 165672199.

991276561 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 991276561 - 2¹¹ = 991274513 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991276501) 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, 45058015 + ... + 45058036.

It is an arithmetic number, because the mean of its divisors is an integer number (270348156).

Almost surely, 2^991276561 is an apocalyptic number.

It is an amenable number.

991276561 is a deficient number, since it is larger than the sum of its proper divisors (90116063).

991276561 is a wasteful number, since it uses less digits than its factorization.

991276561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90116062.

The product of its digits is 204120, while the sum is 46.

The square root of 991276561 is about 31484.5447958201. The cubic root of 991276561 is about 997.0836904060.

The spelling of 991276561 in words is "nine hundred ninety-one million, two hundred seventy-six thousand, five hundred sixty-one".