643687613 has 2 divisors, whose sum is σ = 643687614. Its totient is φ = 643687612.

The previous prime is 643687579. The next prime is 643687651. The reversal of 643687613 is 316786346.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 414407449 + 229280164 = 20357^2 + 15142^2 .

It is a cyclic number.

It is not a de Polignac number, because 643687613 - 2⁶ = 643687549 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643617613) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321843806 + 321843807.

It is an arithmetic number, because the mean of its divisors is an integer number (321843807).

Almost surely, 2^643687613 is an apocalyptic number.

It is an amenable number.

643687613 is a deficient number, since it is larger than the sum of its proper divisors (1).

643687613 is an equidigital number, since it uses as much as digits as its factorization.

643687613 is an evil number, because the sum of its binary digits is even.

The product of its digits is 435456, while the sum is 44.

The square root of 643687613 is about 25370.9994481889. Note that the first 3 decimals coincide. The cubic root of 643687613 is about 863.4258575011.

It can be divided in two parts, 6436 and 87613, that added together give a palindrome (94049).

The spelling of 643687613 in words is "six hundred forty-three million, six hundred eighty-seven thousand, six hundred thirteen".