516717821 has 2 divisors, whose sum is σ = 516717822. Its totient is φ = 516717820.

The previous prime is 516717797. The next prime is 516717823. The reversal of 516717821 is 128717615.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 477204025 + 39513796 = 21845^2 + 6286^2 .

It is a cyclic number.

It is not a de Polignac number, because 516717821 - 2¹⁸ = 516455677 is a prime.

It is a Sophie Germain prime.

Together with 516717823, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (516717823) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 258358910 + 258358911.

It is an arithmetic number, because the mean of its divisors is an integer number (258358911).

Almost surely, 2^516717821 is an apocalyptic number.

It is an amenable number.

516717821 is a deficient number, since it is larger than the sum of its proper divisors (1).

516717821 is an equidigital number, since it uses as much as digits as its factorization.

516717821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 23520, while the sum is 38.

The square root of 516717821 is about 22731.4280457696. The cubic root of 516717821 is about 802.4496895573.

The spelling of 516717821 in words is "five hundred sixteen million, seven hundred seventeen thousand, eight hundred twenty-one".