991811 has 2 divisors, whose sum is σ = 991812. Its totient is φ = 991810.

The previous prime is 991777. The next prime is 991817. The reversal of 991811 is 118199.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 991811 - 2¹⁴ = 975427 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (991817) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495905 + 495906.

It is an arithmetic number, because the mean of its divisors is an integer number (495906).

2⁹⁹¹⁸¹¹ is an apocalyptic number.

991811 is a deficient number, since it is larger than the sum of its proper divisors (1).

991811 is an equidigital number, since it uses as much as digits as its factorization.

991811 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 648, while the sum is 29.

The square root of 991811 is about 995.8970830362. The cubic root of 991811 is about 99.7262848169.

The spelling of 991811 in words is "nine hundred ninety-one thousand, eight hundred eleven".