991618559 has 4 divisors (see below), whose sum is σ = 1006418904. Its totient is φ = 976818216.

The previous prime is 991618543. The next prime is 991618561. The reversal of 991618559 is 955816199.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 955816199 = 13 ⋅73524323.

It is a cyclic number.

It is not a de Polignac number, because 991618559 - 2⁴ = 991618543 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 991618559.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991618259) 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, 7400072 + ... + 7400205.

It is an arithmetic number, because the mean of its divisors is an integer number (251604726).

Almost surely, 2^991618559 is an apocalyptic number.

991618559 is a deficient number, since it is larger than the sum of its proper divisors (14800345).

991618559 is a wasteful number, since it uses less digits than its factorization.

991618559 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14800344.

The product of its digits is 874800, while the sum is 53.

The square root of 991618559 is about 31489.9755319054. The cubic root of 991618559 is about 997.1983443895.

The spelling of 991618559 in words is "nine hundred ninety-one million, six hundred eighteen thousand, five hundred fifty-nine".