640243937 has 2 divisors, whose sum is σ = 640243938. Its totient is φ = 640243936.

The previous prime is 640243909. The next prime is 640243973. The reversal of 640243937 is 739342046.

Together with next prime (640243973) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 596141056 + 44102881 = 24416^2 + 6641^2 .

It is a cyclic number.

It is not a de Polignac number, because 640243937 - 2²² = 636049633 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 640243937.

It is not a weakly prime, because it can be changed into another prime (640243907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320121968 + 320121969.

It is an arithmetic number, because the mean of its divisors is an integer number (320121969).

Almost surely, 2^640243937 is an apocalyptic number.

It is an amenable number.

640243937 is a deficient number, since it is larger than the sum of its proper divisors (1).

640243937 is an equidigital number, since it uses as much as digits as its factorization.

640243937 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 108864, while the sum is 38.

The square root of 640243937 is about 25303.0420503148. The cubic root of 640243937 is about 861.8833509249.

The spelling of 640243937 in words is "six hundred forty million, two hundred forty-three thousand, nine hundred thirty-seven".