309981 has 16 divisors (see below), whose sum is σ = 489600. Its totient is φ = 170688.

The previous prime is 309977. The next prime is 309989. The reversal of 309981 is 189903.

It is a happy number.

It is not a de Polignac number, because 309981 - 2² = 309977 is a prime.

It is a super-2 number, since 2×309981² = 192176440722, which contains 22 as substring.

It is an Ulam 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 309981.

It is not an unprimeable number, because it can be changed into a prime (309989) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 355 + ... + 863.

It is an arithmetic number, because the mean of its divisors is an integer number (30600).

2³⁰⁹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

309981 is a deficient number, since it is larger than the sum of its proper divisors (179619).

309981 is a wasteful number, since it uses less digits than its factorization.

309981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 548.

The product of its (nonzero) digits is 1944, while the sum is 30.

The square root of 309981 is about 556.7593735179. The cubic root of 309981 is about 67.6776118037.

It can be divided in two parts, 30 and 9981, that added together give a triangular number (10011 = T₁₄₁).

The spelling of 309981 in words is "three hundred nine thousand, nine hundred eighty-one".