516821 has 2 divisors, whose sum is σ = 516822. Its totient is φ = 516820.

The previous prime is 516811. The next prime is 516829. The reversal of 516821 is 128615.

516821 is nontrivially palindromic in base 7.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 470596 + 46225 = 686^2 + 215^2 .

It is a cyclic number.

It is not a de Polignac number, because 516821 - 2⁶ = 516757 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (516829) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 258410 + 258411.

It is an arithmetic number, because the mean of its divisors is an integer number (258411).

2⁵¹⁶⁸²¹ is an apocalyptic number.

It is an amenable number.

516821 is a deficient number, since it is larger than the sum of its proper divisors (1).

516821 is an equidigital number, since it uses as much as digits as its factorization.

516821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 480, while the sum is 23.

The square root of 516821 is about 718.9026359668. The cubic root of 516821 is about 80.2503097461.

The spelling of 516821 in words is "five hundred sixteen thousand, eight hundred twenty-one".