640627851 has 4 divisors (see below), whose sum is σ = 854170472. Its totient is φ = 427085232.

The previous prime is 640627843. The next prime is 640627891. The reversal of 640627851 is 158726046.

640627851 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.

It is not a de Polignac number, because 640627851 - 2³ = 640627843 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (640627811) 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, 106771306 + ... + 106771311.

It is an arithmetic number, because the mean of its divisors is an integer number (213542618).

Almost surely, 2^640627851 is an apocalyptic number.

640627851 is a deficient number, since it is larger than the sum of its proper divisors (213542621).

640627851 is a wasteful number, since it uses less digits than its factorization.

640627851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 213542620.

The product of its (nonzero) digits is 80640, while the sum is 39.

The square root of 640627851 is about 25310.6272344247. The cubic root of 640627851 is about 862.0555889058.

The spelling of 640627851 in words is "six hundred forty million, six hundred twenty-seven thousand, eight hundred fifty-one".