646871680 has 256 divisors, whose sum is σ = 1974067200. Its totient is φ = 197148672.

The previous prime is 646871657. The next prime is 646871681. The reversal of 646871680 is 86178646.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 646871680.

It is not an unprimeable number, because it can be changed into a prime (646871681) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1688769 + ... + 1689151.

It is an arithmetic number, because the mean of its divisors is an integer number (7711200).

Almost surely, 2^646871680 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 646871680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (987033600).

646871680 is an abundant number, since it is smaller than the sum of its proper divisors (1327195520).

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

646871680 is a wasteful number, since it uses less digits than its factorization.

646871680 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 451 (or 439 counting only the distinct ones).

The product of its (nonzero) digits is 387072, while the sum is 46.

The square root of 646871680 is about 25433.6721689968. The cubic root of 646871680 is about 864.8471914238.

The spelling of 646871680 in words is "six hundred forty-six million, eight hundred seventy-one thousand, six hundred eighty".