638778243 has 4 divisors (see below), whose sum is σ = 851704328. Its totient is φ = 425852160.

The previous prime is 638778211. The next prime is 638778263. The reversal of 638778243 is 342877836.

638778243 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 638778243 - 2⁵ = 638778211 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 638778192 and 638778201.

It is not an unprimeable number, because it can be changed into a prime (638778263) 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, 106463038 + ... + 106463043.

It is an arithmetic number, because the mean of its divisors is an integer number (212926082).

Almost surely, 2^638778243 is an apocalyptic number.

638778243 is a deficient number, since it is larger than the sum of its proper divisors (212926085).

638778243 is a wasteful number, since it uses less digits than its factorization.

638778243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 212926084.

The product of its digits is 1354752, while the sum is 48.

The square root of 638778243 is about 25274.0626532420. The cubic root of 638778243 is about 861.2251525978.

The spelling of 638778243 in words is "six hundred thirty-eight million, seven hundred seventy-eight thousand, two hundred forty-three".