646868778 has 16 divisors (see below), whose sum is σ = 1294042176. Its totient is φ = 215572160.

The previous prime is 646868773. The next prime is 646868779. The reversal of 646868778 is 877868646.

It is a super-3 number, since 3×646868778³ (a number of 27 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (646868771) 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, 22363 + ... + 42353.

It is an arithmetic number, because the mean of its divisors is an integer number (80877636).

Almost surely, 2^646868778 is an apocalyptic number.

646868778 is an abundant number, since it is smaller than the sum of its proper divisors (647173398).

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

646868778 is a wasteful number, since it uses less digits than its factorization.

646868778 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 25389.

The product of its digits is 21676032, while the sum is 60.

The square root of 646868778 is about 25433.6151185788. The cubic root of 646868778 is about 864.8458981274.

The spelling of 646868778 in words is "six hundred forty-six million, eight hundred sixty-eight thousand, seven hundred seventy-eight".