640306787 has 4 divisors (see below), whose sum is σ = 640413840. Its totient is φ = 640199736.

The previous prime is 640306781. The next prime is 640306801. The reversal of 640306787 is 787603046.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 787603046 = 2 ⋅393801523.

It is a cyclic number.

It is not a de Polignac number, because 640306787 - 2²² = 636112483 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640306781) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 43988 + ... + 56705.

It is an arithmetic number, because the mean of its divisors is an integer number (160103460).

Almost surely, 2^640306787 is an apocalyptic number.

640306787 is a deficient number, since it is larger than the sum of its proper divisors (107053).

640306787 is a wasteful number, since it uses less digits than its factorization.

640306787 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 107052.

The product of its (nonzero) digits is 169344, while the sum is 41.

The square root of 640306787 is about 25304.2839653684. The cubic root of 640306787 is about 861.9115524655.

The spelling of 640306787 in words is "six hundred forty million, three hundred six thousand, seven hundred eighty-seven".