646721655228 has 864 divisors, whose sum is σ = 2042250537600. Its totient is φ = 171730944000.

The previous prime is 646721655143. The next prime is 646721655259. The reversal of 646721655228 is 822556127646.

646721655228 is a `hidden beast` number, since 6 + 4 + 6 + 72 + 16 + 552 + 2 + 8 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 287 ways as a sum of consecutive naturals, for example, 7266535408 + ... + 7266535496.

It is an arithmetic number, because the mean of its divisors is an integer number (2363715900).

Almost surely, 2^646721655228 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 646721655228, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1021125268800).

646721655228 is an abundant number, since it is smaller than the sum of its proper divisors (1395528882372).

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

646721655228 is a wasteful number, since it uses less digits than its factorization.

646721655228 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 275 (or 259 counting only the distinct ones).

The product of its digits is 9676800, while the sum is 54.

The spelling of 646721655228 in words is "six hundred forty-six billion, seven hundred twenty-one million, six hundred fifty-five thousand, two hundred twenty-eight".