991817 has 2 divisors, whose sum is σ = 991818. Its totient is φ = 991816.

The previous prime is 991811. The next prime is 991867. The reversal of 991817 is 718199.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 732736 + 259081 = 856^2 + 509^2 .

It is a cyclic number.

It is not a de Polignac number, because 991817 - 2¹⁴ = 975433 is a prime.

It is a super-2 number, since 2×991817² = 1967401922978, which contains 22 as substring.

It is a Chen prime.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 991817.

It is not a weakly prime, because it can be changed into another prime (991811) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495908 + 495909.

It is an arithmetic number, because the mean of its divisors is an integer number (495909).

2⁹⁹¹⁸¹⁷ is an apocalyptic number.

It is an amenable number.

991817 is a deficient number, since it is larger than the sum of its proper divisors (1).

991817 is an equidigital number, since it uses as much as digits as its factorization.

991817 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 4536, while the sum is 35.

The square root of 991817 is about 995.9000953911. The cubic root of 991817 is about 99.7264859158.

The spelling of 991817 in words is "nine hundred ninety-one thousand, eight hundred seventeen".