640661519 has 2 divisors, whose sum is σ = 640661520. Its totient is φ = 640661518.

The previous prime is 640661501. The next prime is 640661597. The reversal of 640661519 is 915166046.

It is a weak prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-640661519 is a prime.

It is a super-2 number, since 2×640661519² = 820894363854774722, which contains 22 as substring.

It is a Sophie Germain 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 (640663519) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 320330759 + 320330760.

It is an arithmetic number, because the mean of its divisors is an integer number (320330760).

Almost surely, 2^640661519 is an apocalyptic number.

640661519 is a deficient number, since it is larger than the sum of its proper divisors (1).

640661519 is an equidigital number, since it uses as much as digits as its factorization.

640661519 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 38880, while the sum is 38.

The square root of 640661519 is about 25311.2923218077. The cubic root of 640661519 is about 862.0706903302.

The spelling of 640661519 in words is "six hundred forty million, six hundred sixty-one thousand, five hundred nineteen".