640897787 has 2 divisors, whose sum is σ = 640897788. Its totient is φ = 640897786.

The previous prime is 640897771. The next prime is 640897801. The reversal of 640897787 is 787798046.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 640897787 - 2⁴ = 640897771 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (640897087) 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, 320448893 + 320448894.

It is an arithmetic number, because the mean of its divisors is an integer number (320448894).

Almost surely, 2^640897787 is an apocalyptic number.

640897787 is a deficient number, since it is larger than the sum of its proper divisors (1).

640897787 is an equidigital number, since it uses as much as digits as its factorization.

640897787 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4741632, while the sum is 56.

The square root of 640897787 is about 25315.9591364815. The cubic root of 640897787 is about 862.1766509551.

The spelling of 640897787 in words is "six hundred forty million, eight hundred ninety-seven thousand, seven hundred eighty-seven".