640420757 has 2 divisors, whose sum is σ = 640420758. Its totient is φ = 640420756.

The previous prime is 640420733. The next prime is 640420777. The reversal of 640420757 is 757024046.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 547606801 + 92813956 = 23401^2 + 9634^2 .

It is a cyclic number.

It is not a de Polignac number, because 640420757 - 2²² = 636226453 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (640420777) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320210378 + 320210379.

It is an arithmetic number, because the mean of its divisors is an integer number (320210379).

Almost surely, 2^640420757 is an apocalyptic number.

It is an amenable number.

640420757 is a deficient number, since it is larger than the sum of its proper divisors (1).

640420757 is an equidigital number, since it uses as much as digits as its factorization.

640420757 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 47040, while the sum is 35.

The square root of 640420757 is about 25306.5358553872. The cubic root of 640420757 is about 861.9626874495.

The spelling of 640420757 in words is "six hundred forty million, four hundred twenty thousand, seven hundred fifty-seven".