639663378 has 16 divisors (see below), whose sum is σ = 1279687296. Its totient is φ = 213161040.

The previous prime is 639663377. The next prime is 639663379. The reversal of 639663378 is 873366936.

It is a happy number.

It is an interprime number because it is at equal distance from previous prime (639663377) and next prime (639663379).

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 639663378.

It is not an unprimeable number, because it can be changed into a prime (639663377) 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, 11700 + ... + 37632.

It is an arithmetic number, because the mean of its divisors is an integer number (79980456).

Almost surely, 2^639663378 is an apocalyptic number.

639663378 is an abundant number, since it is smaller than the sum of its proper divisors (640023918).

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

639663378 is a wasteful number, since it uses less digits than its factorization.

639663378 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 30049.

The product of its digits is 2939328, while the sum is 51.

The square root of 639663378 is about 25291.5673298434. The cubic root of 639663378 is about 861.6227599083.

The spelling of 639663378 in words is "six hundred thirty-nine million, six hundred sixty-three thousand, three hundred seventy-eight".