991187 has 2 divisors, whose sum is σ = 991188. Its totient is φ = 991186.

The previous prime is 991181. The next prime is 991201. The reversal of 991187 is 781199.

It is a weak prime.

It is an emirp because it is prime and its reverse (781199) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 991187 - 2⁴ = 991171 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (991181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 495593 + 495594.

It is an arithmetic number, because the mean of its divisors is an integer number (495594).

2⁹⁹¹¹⁸⁷ is an apocalyptic number.

991187 is a deficient number, since it is larger than the sum of its proper divisors (1).

991187 is an equidigital number, since it uses as much as digits as its factorization.

991187 is an evil number, because the sum of its binary digits is even.

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

The square root of 991187 is about 995.5837483607. The cubic root of 991187 is about 99.7053660945.

The spelling of 991187 in words is "nine hundred ninety-one thousand, one hundred eighty-seven".