640978859 has 2 divisors, whose sum is σ = 640978860. Its totient is φ = 640978858.

The previous prime is 640978837. The next prime is 640978879. The reversal of 640978859 is 958879046.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 640978859 - 2²⁸ = 372543403 is a prime.

It is not a weakly prime, because it can be changed into another prime (640978879) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320489429 + 320489430.

It is an arithmetic number, because the mean of its divisors is an integer number (320489430).

Almost surely, 2^640978859 is an apocalyptic number.

640978859 is a deficient number, since it is larger than the sum of its proper divisors (1).

640978859 is an equidigital number, since it uses as much as digits as its factorization.

640978859 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 4354560, while the sum is 56.

The square root of 640978859 is about 25317.5602892538. The cubic root of 640978859 is about 862.2130038337.

The spelling of 640978859 in words is "six hundred forty million, nine hundred seventy-eight thousand, eight hundred fifty-nine".