Adding to 643 its sum of digits (13), we get a palindrome (656).
Subtracting from 643 its sum of digits (13), we obtain a triangular number (630 = T35).
Adding to 643 its reverse (346), we get a palindrome (989).
643 is nontrivially palindromic in base 11.
It is a weak prime.
643 is a truncatable prime.
It is a cyclic number.
643 is an undulating number in base 11.
643 is a lucky number.
It is a plaindrome in base 12, base 14 and base 15.
It is a nialpdrome in base 10.
643 is an equidigital number, since it uses as much as digits as its factorization.
643 is an evil number, because the sum of its binary digits is even.
The square root of 643 is about 25.3574446662. The cubic root of 643 is about 8.6311829922.
The spelling of 643 in words is "six hundred forty-three", and thus it is an aban number.