640321009 has 2 divisors, whose sum is σ = 640321010. Its totient is φ = 640321008.

The previous prime is 640320953. The next prime is 640321039. The reversal of 640321009 is 900123046.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 499969600 + 140351409 = 22360^2 + 11847^2 .

It is a cyclic number.

It is not a de Polignac number, because 640321009 - 2¹³ = 640312817 is a prime.

It is not a weakly prime, because it can be changed into another prime (640321039) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320160504 + 320160505.

It is an arithmetic number, because the mean of its divisors is an integer number (320160505).

Almost surely, 2^640321009 is an apocalyptic number.

It is an amenable number.

640321009 is a deficient number, since it is larger than the sum of its proper divisors (1).

640321009 is an equidigital number, since it uses as much as digits as its factorization.

640321009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1296, while the sum is 25.

The square root of 640321009 is about 25304.5649834175. The cubic root of 640321009 is about 861.9179337896.

The spelling of 640321009 in words is "six hundred forty million, three hundred twenty-one thousand, nine".