991660811 has 2 divisors, whose sum is σ = 991660812. Its totient is φ = 991660810.

The previous prime is 991660781. The next prime is 991660853. The reversal of 991660811 is 118066199.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 991660811 - 2²² = 987466507 is a prime.

It is not a weakly prime, because it can be changed into another prime (991660211) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495830405 + 495830406.

It is an arithmetic number, because the mean of its divisors is an integer number (495830406).

Almost surely, 2^991660811 is an apocalyptic number.

991660811 is a deficient number, since it is larger than the sum of its proper divisors (1).

991660811 is an equidigital number, since it uses as much as digits as its factorization.

991660811 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 23328, while the sum is 41.

The square root of 991660811 is about 31490.6464049247. The cubic root of 991660811 is about 997.2125074383.

The spelling of 991660811 in words is "nine hundred ninety-one million, six hundred sixty thousand, eight hundred eleven".