281991 has 4 divisors (see below), whose sum is σ = 375992. Its totient is φ = 187992.

The previous prime is 281989. The next prime is 281993. The reversal of 281991 is 199182.

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

It is an interprime number because it is at equal distance from previous prime (281989) and next prime (281993).

It is not a de Polignac number, because 281991 - 2¹ = 281989 is a prime.

It is a D-number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (281993) 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, 46996 + ... + 47001.

It is an arithmetic number, because the mean of its divisors is an integer number (93998).

2²⁸¹⁹⁹¹ is an apocalyptic number.

281991 is a deficient number, since it is larger than the sum of its proper divisors (94001).

281991 is an equidigital number, since it uses as much as digits as its factorization.

281991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 94000.

The product of its digits is 1296, while the sum is 30.

The square root of 281991 is about 531.0282478362. The cubic root of 281991 is about 65.5760242296.

Subtracting from 281991 its sum of digits (30), we obtain a square (281961 = 531²).

The spelling of 281991 in words is "two hundred eighty-one thousand, nine hundred ninety-one".