643717636 has 12 divisors (see below), whose sum is σ = 1126995660. Its totient is φ = 321718880.

The previous prime is 643717621. The next prime is 643717637. The reversal of 643717636 is 636717346.

It can be written as a sum of positive squares in 2 ways, for example, as 109830400 + 533887236 = 10480^2 + 23106^2 .

It is a junction number, because it is equal to n+sod(n) for n = 643717592 and 643717601.

It is not an unprimeable number, because it can be changed into a prime (643717637) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 24271 + ... + 43318.

It is an arithmetic number, because the mean of its divisors is an integer number (93916305).

Almost surely, 2^643717636 is an apocalyptic number.

It is an amenable number.

643717636 is a deficient number, since it is larger than the sum of its proper divisors (483278024).

643717636 is a wasteful number, since it uses less digits than its factorization.

643717636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 69974 (or 69972 counting only the distinct ones).

The product of its digits is 381024, while the sum is 43.

The square root of 643717636 is about 25371.5911207792. The cubic root of 643717636 is about 863.4392813167.

The spelling of 643717636 in words is "six hundred forty-three million, seven hundred seventeen thousand, six hundred thirty-six".