643123421 has 2 divisors, whose sum is σ = 643123422. Its totient is φ = 643123420.

The previous prime is 643123391. The next prime is 643123463. The reversal of 643123421 is 124321346.

643123421 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 400200025 + 242923396 = 20005^2 + 15586^2 .

It is a cyclic number.

It is not a de Polignac number, because 643123421 - 2¹⁸ = 642861277 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (643123471) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321561710 + 321561711.

It is an arithmetic number, because the mean of its divisors is an integer number (321561711).

Almost surely, 2^643123421 is an apocalyptic number.

It is an amenable number.

643123421 is a deficient number, since it is larger than the sum of its proper divisors (1).

643123421 is an equidigital number, since it uses as much as digits as its factorization.

643123421 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3456, while the sum is 26.

The square root of 643123421 is about 25359.8781739976. The cubic root of 643123421 is about 863.1735195935.

Adding to 643123421 its reverse (124321346), we get a palindrome (767444767).

The spelling of 643123421 in words is "six hundred forty-three million, one hundred twenty-three thousand, four hundred twenty-one".