187981 has 4 divisors (see below), whose sum is σ = 188892. Its totient is φ = 187072.

The previous prime is 187973. The next prime is 187987. The reversal of 187981 is 189781.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length, and also an emirpimes, since its reverse is a distinct semiprime: 189781 = 173 ⋅1097.

It can be written as a sum of positive squares in 2 ways, for example, as 54756 + 133225 = 234^2 + 365^2 .

It is a cyclic number.

It is not a de Polignac number, because 187981 - 2³ = 187973 is a prime.

It is a super-2 number, since 2×187981² = 70673712722, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (187987) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 21 + ... + 613.

It is an arithmetic number, because the mean of its divisors is an integer number (47223).

2¹⁸⁷⁹⁸¹ is an apocalyptic number.

It is an amenable number.

187981 is a deficient number, since it is larger than the sum of its proper divisors (911).

187981 is an equidigital number, since it uses as much as digits as its factorization.

187981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 910.

The product of its digits is 4032, while the sum is 34.

The square root of 187981 is about 433.5677571038. The cubic root of 187981 is about 57.2846132290.

The spelling of 187981 in words is "one hundred eighty-seven thousand, nine hundred eighty-one".