640644656543 has 2 divisors, whose sum is σ = 640644656544. Its totient is φ = 640644656542.

The previous prime is 640644656521. The next prime is 640644656557. The reversal of 640644656543 is 345656446046.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 640644656543 - 2⁸ = 640644656287 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640644656513) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320322328271 + 320322328272.

It is an arithmetic number, because the mean of its divisors is an integer number (320322328272).

Almost surely, 2^640644656543 is an apocalyptic number.

640644656543 is a deficient number, since it is larger than the sum of its proper divisors (1).

640644656543 is an equidigital number, since it uses as much as digits as its factorization.

640644656543 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 24883200, while the sum is 53.

The spelling of 640644656543 in words is "six hundred forty billion, six hundred forty-four million, six hundred fifty-six thousand, five hundred forty-three".