643643123 has 2 divisors, whose sum is σ = 643643124. Its totient is φ = 643643122.

The previous prime is 643643113. The next prime is 643643131. The reversal of 643643123 is 321346346.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 643643123 - 2¹⁰ = 643642099 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 643643123.

It is not a weakly prime, because it can be changed into another prime (643643113) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 321821561 + 321821562.

It is an arithmetic number, because the mean of its divisors is an integer number (321821562).

Almost surely, 2^643643123 is an apocalyptic number.

643643123 is a deficient number, since it is larger than the sum of its proper divisors (1).

643643123 is an equidigital number, since it uses as much as digits as its factorization.

643643123 is an evil number, because the sum of its binary digits is even.

The product of its digits is 31104, while the sum is 32.

The square root of 643643123 is about 25370.1226445597. The cubic root of 643643123 is about 863.4059644657.

Adding to 643643123 its reverse (321346346), we get a palindrome (964989469).

The spelling of 643643123 in words is "six hundred forty-three million, six hundred forty-three thousand, one hundred twenty-three".