509981 has 4 divisors (see below), whose sum is σ = 526464. Its totient is φ = 493500.

The previous prime is 509963. The next prime is 509989. The reversal of 509981 is 189905.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 509981 - 2¹⁰ = 508957 is a prime.

It is a super-2 number, since 2×509981² = 520161240722, 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 (509989) 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, 8195 + ... + 8256.

It is an arithmetic number, because the mean of its divisors is an integer number (131616).

2⁵⁰⁹⁹⁸¹ is an apocalyptic number.

It is an amenable number.

509981 is a deficient number, since it is larger than the sum of its proper divisors (16483).

509981 is a wasteful number, since it uses less digits than its factorization.

509981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 16482.

The product of its (nonzero) digits is 3240, while the sum is 32.

The square root of 509981 is about 714.1295400696. The cubic root of 509981 is about 79.8947052234.

The spelling of 509981 in words is "five hundred nine thousand, nine hundred eighty-one".