638685378 has 16 divisors (see below), whose sum is σ = 1419300960. Its totient is φ = 212895108.

The previous prime is 638685373. The next prime is 638685389. The reversal of 638685378 is 873586836.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (54), and also a Moran number because the ratio is a prime number: 11827507 = 638685378 / (6 + 3 + 8 + 6 + 8 + 5 + 3 + 7 + 8).

It is not an unprimeable number, because it can be changed into a prime (638685373) 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, 5913700 + ... + 5913807.

It is an arithmetic number, because the mean of its divisors is an integer number (88706310).

Almost surely, 2^638685378 is an apocalyptic number.

638685378 is an abundant number, since it is smaller than the sum of its proper divisors (780615582).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

638685378 is a wasteful number, since it uses less digits than its factorization.

638685378 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11827518 (or 11827512 counting only the distinct ones).

The product of its digits is 5806080, while the sum is 54.

The square root of 638685378 is about 25272.2254263450. The cubic root of 638685378 is about 861.1834158653.

The spelling of 638685378 in words is "six hundred thirty-eight million, six hundred eighty-five thousand, three hundred seventy-eight".