640908857551 has 2 divisors, whose sum is σ = 640908857552. Its totient is φ = 640908857550.

The previous prime is 640908857531. The next prime is 640908857581. The reversal of 640908857551 is 155758809046.

It is a happy number.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 640908857551 - 2²⁷ = 640774639823 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640908857531) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320454428775 + 320454428776.

It is an arithmetic number, because the mean of its divisors is an integer number (320454428776).

Almost surely, 2^640908857551 is an apocalyptic number.

640908857551 is a deficient number, since it is larger than the sum of its proper divisors (1).

640908857551 is an equidigital number, since it uses as much as digits as its factorization.

640908857551 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 12096000, while the sum is 58.

The spelling of 640908857551 in words is "six hundred forty billion, nine hundred eight million, eight hundred fifty-seven thousand, five hundred fifty-one".