642716813 has 2 divisors, whose sum is σ = 642716814. Its totient is φ = 642716812.

The previous prime is 642716783. The next prime is 642716839. The reversal of 642716813 is 318617246.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 642216964 + 499849 = 25342^2 + 707^2 .

It is a cyclic number.

It is not a de Polignac number, because 642716813 - 2¹⁶ = 642651277 is a prime.

It is a Sophie Germain 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 (642716843) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321358406 + 321358407.

It is an arithmetic number, because the mean of its divisors is an integer number (321358407).

Almost surely, 2^642716813 is an apocalyptic number.

It is an amenable number.

642716813 is a deficient number, since it is larger than the sum of its proper divisors (1).

642716813 is an equidigital number, since it uses as much as digits as its factorization.

642716813 is an evil number, because the sum of its binary digits is even.

The product of its digits is 48384, while the sum is 38.

The square root of 642716813 is about 25351.8601487149. The cubic root of 642716813 is about 862.9915704583.

The spelling of 642716813 in words is "six hundred forty-two million, seven hundred sixteen thousand, eight hundred thirteen".