646819568640 has 2112 divisors, whose sum is σ = 2921492810880. Its totient is φ = 134762987520.

The previous prime is 646819568639. The next prime is 646819568641. The reversal of 646819568640 is 46865918646.

646819568640 is a `hidden beast` number, since 6 + 4 + 6 + 8 + 1 + 9 + 568 + 64 + 0 = 666.

It is an interprime number because it is at equal distance from previous prime (646819568639) and next prime (646819568641).

It is a Harshad number since it is a multiple of its sum of digits (63).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646819568641) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 191 ways as a sum of consecutive naturals, for example, 4721310652 + ... + 4721310788.

Almost surely, 2^646819568640 is an apocalyptic number.

646819568640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 646819568640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1460746405440).

646819568640 is an abundant number, since it is smaller than the sum of its proper divisors (2274673242240).

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

646819568640 is a wasteful number, since it uses less digits than its factorization.

646819568640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 243 (or 212 counting only the distinct ones).

The product of its (nonzero) digits is 59719680, while the sum is 63.

The spelling of 646819568640 in words is "six hundred forty-six billion, eight hundred nineteen million, five hundred sixty-eight thousand, six hundred forty".