816617991 has 16 divisors (see below), whose sum is σ = 1246880000. Its totient is φ = 465697728.

The previous prime is 816617981. The next prime is 816617999. The reversal of 816617991 is 199716618.

It is not a de Polignac number, because 816617991 - 2¹⁹ = 816093703 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 816617991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (816617999) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 28486 + ... + 49443.

It is an arithmetic number, because the mean of its divisors is an integer number (77930000).

Almost surely, 2^816617991 is an apocalyptic number.

816617991 is a deficient number, since it is larger than the sum of its proper divisors (430262009).

816617991 is a wasteful number, since it uses less digits than its factorization.

816617991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78438.

The product of its digits is 163296, while the sum is 48.

The square root of 816617991 is about 28576.5286730212. The cubic root of 816617991 is about 934.7015895010.

The spelling of 816617991 in words is "eight hundred sixteen million, six hundred seventeen thousand, nine hundred ninety-one".