640717786 has 16 divisors (see below), whose sum is σ = 972080424. Its totient is φ = 316698624.

The previous prime is 640717751. The next prime is 640717787. The reversal of 640717786 is 687717046.

It can be written as a sum of positive squares in 4 ways, for example, as 631567161 + 9150625 = 25131^2 + 3025^2 .

It is not an unprimeable number, because it can be changed into a prime (640717787) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 280746 + ... + 283018.

Almost surely, 2^640717786 is an apocalyptic number.

640717786 is a deficient number, since it is larger than the sum of its proper divisors (331362638).

640717786 is a wasteful number, since it uses less digits than its factorization.

640717786 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3825.

The product of its (nonzero) digits is 395136, while the sum is 46.

The square root of 640717786 is about 25312.4037973481. The cubic root of 640717786 is about 862.0959271154.

The spelling of 640717786 in words is "six hundred forty million, seven hundred seventeen thousand, seven hundred eighty-six".