640545109 has 2 divisors, whose sum is σ = 640545110. Its totient is φ = 640545108.

The previous prime is 640545097. The next prime is 640545151. The reversal of 640545109 is 901545046.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 622652209 + 17892900 = 24953^2 + 4230^2 .

It is a cyclic number.

It is not a de Polignac number, because 640545109 - 2¹¹ = 640543061 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640542109) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320272554 + 320272555.

It is an arithmetic number, because the mean of its divisors is an integer number (320272555).

Almost surely, 2^640545109 is an apocalyptic number.

It is an amenable number.

640545109 is a deficient number, since it is larger than the sum of its proper divisors (1).

640545109 is an equidigital number, since it uses as much as digits as its factorization.

640545109 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 21600, while the sum is 34.

The square root of 640545109 is about 25308.9926508346. The cubic root of 640545109 is about 862.0184736110.

The spelling of 640545109 in words is "six hundred forty million, five hundred forty-five thousand, one hundred nine".