640544893 has 2 divisors, whose sum is σ = 640544894. Its totient is φ = 640544892.

The previous prime is 640544867. The next prime is 640544923. The reversal of 640544893 is 398445046.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 516289284 + 124255609 = 22722^2 + 11147^2 .

It is a cyclic number.

It is not a de Polignac number, because 640544893 - 2⁹ = 640544381 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640544393) 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, 320272446 + 320272447.

It is an arithmetic number, because the mean of its divisors is an integer number (320272447).

Almost surely, 2^640544893 is an apocalyptic number.

It is an amenable number.

640544893 is a deficient number, since it is larger than the sum of its proper divisors (1).

640544893 is an equidigital number, since it uses as much as digits as its factorization.

640544893 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 414720, while the sum is 43.

The square root of 640544893 is about 25308.9883835763. The cubic root of 640544893 is about 862.0183767164.

The spelling of 640544893 in words is "six hundred forty million, five hundred forty-four thousand, eight hundred ninety-three".