640628123 has 2 divisors, whose sum is σ = 640628124. Its totient is φ = 640628122.

The previous prime is 640628099. The next prime is 640628159. The reversal of 640628123 is 321826046.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640628123 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 640628123.

It is not a weakly prime, because it can be changed into another prime (640622123) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320314061 + 320314062.

It is an arithmetic number, because the mean of its divisors is an integer number (320314062).

Almost surely, 2^640628123 is an apocalyptic number.

640628123 is a deficient number, since it is larger than the sum of its proper divisors (1).

640628123 is an equidigital number, since it uses as much as digits as its factorization.

640628123 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 13824, while the sum is 32.

The square root of 640628123 is about 25310.6326076612. The cubic root of 640628123 is about 862.0557109106.

The spelling of 640628123 in words is "six hundred forty million, six hundred twenty-eight thousand, one hundred twenty-three".