640895639 has 2 divisors, whose sum is σ = 640895640. Its totient is φ = 640895638.

The previous prime is 640895599. The next prime is 640895657. The reversal of 640895639 is 936598046.

640895639 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 640895639 - 2¹⁶ = 640830103 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640895839) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320447819 + 320447820.

It is an arithmetic number, because the mean of its divisors is an integer number (320447820).

Almost surely, 2^640895639 is an apocalyptic number.

640895639 is a deficient number, since it is larger than the sum of its proper divisors (1).

640895639 is an equidigital number, since it uses as much as digits as its factorization.

640895639 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1399680, while the sum is 50.

The square root of 640895639 is about 25315.9167126138. The cubic root of 640895639 is about 862.1756877451.

The spelling of 640895639 in words is "six hundred forty million, eight hundred ninety-five thousand, six hundred thirty-nine".