640738771 has 4 divisors (see below), whose sum is σ = 640859632. Its totient is φ = 640617912.

The previous prime is 640738751. The next prime is 640738781. The reversal of 640738771 is 177837046.

640738771 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 177837046 = 2 ⋅88918523.

It is a cyclic number.

It is not a de Polignac number, because 640738771 - 2²⁹ = 103867859 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640738741) 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, 52095 + ... + 63208.

It is an arithmetic number, because the mean of its divisors is an integer number (160214908).

Almost surely, 2^640738771 is an apocalyptic number.

640738771 is a deficient number, since it is larger than the sum of its proper divisors (120861).

640738771 is a wasteful number, since it uses less digits than its factorization.

640738771 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 120860.

The product of its (nonzero) digits is 197568, while the sum is 43.

The square root of 640738771 is about 25312.8183140479. The cubic root of 640738771 is about 862.1053388960.

The spelling of 640738771 in words is "six hundred forty million, seven hundred thirty-eight thousand, seven hundred seventy-one".