643784689 has 2 divisors, whose sum is σ = 643784690. Its totient is φ = 643784688.

The previous prime is 643784683. The next prime is 643784699. The reversal of 643784689 is 986487346.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 417793600 + 225991089 = 20440^2 + 15033^2 .

It is a cyclic number.

It is not a de Polignac number, because 643784689 - 2³ = 643784681 is a prime.

It is not a weakly prime, because it can be changed into another prime (643784681) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321892344 + 321892345.

It is an arithmetic number, because the mean of its divisors is an integer number (321892345).

Almost surely, 2^643784689 is an apocalyptic number.

It is an amenable number.

643784689 is a deficient number, since it is larger than the sum of its proper divisors (1).

643784689 is an equidigital number, since it uses as much as digits as its factorization.

643784689 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6967296, while the sum is 55.

The square root of 643784689 is about 25372.9125052683. The cubic root of 643784689 is about 863.4692603949.

The spelling of 643784689 in words is "six hundred forty-three million, seven hundred eighty-four thousand, six hundred eighty-nine".