643542643 has 2 divisors, whose sum is σ = 643542644. Its totient is φ = 643542642.

The previous prime is 643542637. The next prime is 643542689. The reversal of 643542643 is 346245346.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 643542643 - 2²⁹ = 106671731 is a prime.

It is not a weakly prime, because it can be changed into another prime (643542623) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321771321 + 321771322.

It is an arithmetic number, because the mean of its divisors is an integer number (321771322).

Almost surely, 2^643542643 is an apocalyptic number.

643542643 is a deficient number, since it is larger than the sum of its proper divisors (1).

643542643 is an equidigital number, since it uses as much as digits as its factorization.

643542643 is an evil number, because the sum of its binary digits is even.

The product of its digits is 207360, while the sum is 37.

The square root of 643542643 is about 25368.1422851576. The cubic root of 643542643 is about 863.3610329692.

Adding to 643542643 its reverse (346245346), we get a palindrome (989787989).

The spelling of 643542643 in words is "six hundred forty-three million, five hundred forty-two thousand, six hundred forty-three".