991902187 has 4 divisors (see below), whose sum is σ = 997443720. Its totient is φ = 986360656.

The previous prime is 991902161. The next prime is 991902211. The reversal of 991902187 is 781209199.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 991902187 - 2⁷ = 991902059 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (991902127) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2770498 + ... + 2770855.

It is an arithmetic number, because the mean of its divisors is an integer number (249360930).

Almost surely, 2^991902187 is an apocalyptic number.

991902187 is a deficient number, since it is larger than the sum of its proper divisors (5541533).

991902187 is a wasteful number, since it uses less digits than its factorization.

991902187 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 5541532.

The product of its (nonzero) digits is 81648, while the sum is 46.

The square root of 991902187 is about 31494.4786748408. The cubic root of 991902187 is about 997.2934099796.

The spelling of 991902187 in words is "nine hundred ninety-one million, nine hundred two thousand, one hundred eighty-seven".