991867 has 2 divisors, whose sum is σ = 991868. Its totient is φ = 991866.

The previous prime is 991817. The next prime is 991871. The reversal of 991867 is 768199.

It is a strong prime.

It is an emirp because it is prime and its reverse (768199) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 991867 - 2¹⁵ = 959099 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, 495933 + 495934.

It is an arithmetic number, because the mean of its divisors is an integer number (495934).

2⁹⁹¹⁸⁶⁷ is an apocalyptic number.

991867 is a deficient number, since it is larger than the sum of its proper divisors (1).

991867 is an equidigital number, since it uses as much as digits as its factorization.

991867 is an evil number, because the sum of its binary digits is even.

The product of its digits is 27216, while the sum is 40.

The square root of 991867 is about 995.9251979943. The cubic root of 991867 is about 99.7281617090.

The spelling of 991867 in words is "nine hundred ninety-one thousand, eight hundred sixty-seven".