638647851 has 4 divisors (see below), whose sum is σ = 851530472. Its totient is φ = 425765232.

The previous prime is 638647829. The next prime is 638647859. The reversal of 638647851 is 158746836.

638647851 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 638647851 - 2¹⁴ = 638631467 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 638647851.

It is not an unprimeable number, because it can be changed into a prime (638647859) 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, 106441306 + ... + 106441311.

It is an arithmetic number, because the mean of its divisors is an integer number (212882618).

Almost surely, 2^638647851 is an apocalyptic number.

638647851 is a deficient number, since it is larger than the sum of its proper divisors (212882621).

638647851 is a wasteful number, since it uses less digits than its factorization.

638647851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 212882620.

The product of its digits is 967680, while the sum is 48.

The square root of 638647851 is about 25271.4829600481. The cubic root of 638647851 is about 861.1665487901.

The spelling of 638647851 in words is "six hundred thirty-eight million, six hundred forty-seven thousand, eight hundred fifty-one".