640751009 has 2 divisors, whose sum is σ = 640751010. Its totient is φ = 640751008.

The previous prime is 640750987. The next prime is 640751099. The reversal of 640751009 is 900157046.

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., 552391009 + 88360000 = 23503^2 + 9400^2 .

It is a cyclic number.

It is not a de Polignac number, because 640751009 - 2⁸ = 640750753 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (640751099) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320375504 + 320375505.

It is an arithmetic number, because the mean of its divisors is an integer number (320375505).

Almost surely, 2^640751009 is an apocalyptic number.

It is an amenable number.

640751009 is a deficient number, since it is larger than the sum of its proper divisors (1).

640751009 is an equidigital number, since it uses as much as digits as its factorization.

640751009 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7560, while the sum is 32.

The square root of 640751009 is about 25313.0600481254. The cubic root of 640751009 is about 862.1108275488.

The spelling of 640751009 in words is "six hundred forty million, seven hundred fifty-one thousand, nine".