640736687 has 2 divisors, whose sum is σ = 640736688. Its totient is φ = 640736686.

The previous prime is 640736671. The next prime is 640736693. The reversal of 640736687 is 786637046.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 640736687 - 2⁴ = 640736671 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640736617) 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, 320368343 + 320368344.

It is an arithmetic number, because the mean of its divisors is an integer number (320368344).

Almost surely, 2^640736687 is an apocalyptic number.

640736687 is a deficient number, since it is larger than the sum of its proper divisors (1).

640736687 is an equidigital number, since it uses as much as digits as its factorization.

640736687 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1016064, while the sum is 47.

The square root of 640736687 is about 25312.7771491000. Note that the first 3 decimals coincide. The cubic root of 640736687 is about 862.1044042304.

The spelling of 640736687 in words is "six hundred forty million, seven hundred thirty-six thousand, six hundred eighty-seven".