305981 has 4 divisors (see below), whose sum is σ = 329532. Its totient is φ = 282432.

The previous prime is 305971. The next prime is 305999. The reversal of 305981 is 189503.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 189503 = 31 ⋅6113.

It can be written as a sum of positive squares in 2 ways, for example, as 70756 + 235225 = 266^2 + 485^2 .

It is a cyclic number.

It is not a de Polignac number, because 305981 - 2⁶ = 305917 is a prime.

It is a super-2 number, since 2×305981² = 187248744722, which contains 22 as substring.

It is an Ulam number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 305981.

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 305981.

It is not an unprimeable number, because it can be changed into a prime (305971) 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, 11756 + ... + 11781.

It is an arithmetic number, because the mean of its divisors is an integer number (82383).

2³⁰⁵⁹⁸¹ is an apocalyptic number.

It is an amenable number.

305981 is a deficient number, since it is larger than the sum of its proper divisors (23551).

305981 is a wasteful number, since it uses less digits than its factorization.

305981 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 23550.

The product of its (nonzero) digits is 1080, while the sum is 26.

The square root of 305981 is about 553.1554935097. The cubic root of 305981 is about 67.3852462666.

The spelling of 305981 in words is "three hundred five thousand, nine hundred eighty-one".