643707637 has 2 divisors, whose sum is σ = 643707638. Its totient is φ = 643707636.

The previous prime is 643707557. The next prime is 643707671. The reversal of 643707637 is 736707346.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 635493681 + 8213956 = 25209^2 + 2866^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-643707637 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 643707593 and 643707602.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643707677) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321853818 + 321853819.

It is an arithmetic number, because the mean of its divisors is an integer number (321853819).

Almost surely, 2^643707637 is an apocalyptic number.

It is an amenable number.

643707637 is a deficient number, since it is larger than the sum of its proper divisors (1).

643707637 is an equidigital number, since it uses as much as digits as its factorization.

643707637 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 444528, while the sum is 43.

The square root of 643707637 is about 25371.3940689115. The cubic root of 643707637 is about 863.4348106329.

The spelling of 643707637 in words is "six hundred forty-three million, seven hundred seven thousand, six hundred thirty-seven".