191987 has 4 divisors (see below), whose sum is σ = 193800. Its totient is φ = 190176.

The previous prime is 191977. The next prime is 191999. The reversal of 191987 is 789191.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-191987 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 191987.

It is not an unprimeable number, because it can be changed into a prime (191977) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 737 + ... + 962.

It is an arithmetic number, because the mean of its divisors is an integer number (48450).

2¹⁹¹⁹⁸⁷ is an apocalyptic number.

191987 is a deficient number, since it is larger than the sum of its proper divisors (1813).

191987 is a wasteful number, since it uses less digits than its factorization.

191987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1812.

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

The square root of 191987 is about 438.1632116004. The cubic root of 191987 is about 57.6886807520.

The spelling of 191987 in words is "one hundred ninety-one thousand, nine hundred eighty-seven".