509721 has 8 divisors (see below), whose sum is σ = 685344. Its totient is φ = 336960.

The previous prime is 509699. The next prime is 509723. The reversal of 509721 is 127905.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 509721 - 2⁵ = 509689 is a prime.

It is a Curzon number.

It is a junction number, because it is equal to n+sod(n) for n = 509691 and 509700.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 509721.

It is not an unprimeable number, because it can be changed into a prime (509723) 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 7 ways as a sum of consecutive naturals, for example, 256 + ... + 1041.

It is an arithmetic number, because the mean of its divisors is an integer number (85668).

2⁵⁰⁹⁷²¹ is an apocalyptic number.

It is an amenable number.

509721 is a deficient number, since it is larger than the sum of its proper divisors (175623).

509721 is a wasteful number, since it uses less digits than its factorization.

509721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1431.

The product of its (nonzero) digits is 630, while the sum is 24.

The square root of 509721 is about 713.9474770598. The cubic root of 509721 is about 79.8811255316.

The spelling of 509721 in words is "five hundred nine thousand, seven hundred twenty-one".