643501637 has 2 divisors, whose sum is σ = 643501638. Its totient is φ = 643501636.

The previous prime is 643501609. The next prime is 643501657. The reversal of 643501637 is 736105346.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 361228036 + 282273601 = 19006^2 + 16801^2 .

It is a cyclic number.

It is not a de Polignac number, because 643501637 - 2²⁴ = 626724421 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 643501597 and 643501606.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643501657) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321750818 + 321750819.

It is an arithmetic number, because the mean of its divisors is an integer number (321750819).

Almost surely, 2^643501637 is an apocalyptic number.

It is an amenable number.

643501637 is a deficient number, since it is larger than the sum of its proper divisors (1).

643501637 is an equidigital number, since it uses as much as digits as its factorization.

643501637 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 45360, while the sum is 35.

The square root of 643501637 is about 25367.3340538575. The cubic root of 643501637 is about 863.3426950316.

The spelling of 643501637 in words is "six hundred forty-three million, five hundred one thousand, six hundred thirty-seven".