646506656640 has 768 divisors, whose sum is σ = 2542656130560. Its totient is φ = 150228172800.

The previous prime is 646506656557. The next prime is 646506656647. The reversal of 646506656640 is 46656605646.

646506656640 is a `hidden beast` number, since 6 + 46 + 506 + 6 + 56 + 6 + 40 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (646506656647) 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 95 ways as a sum of consecutive naturals, for example, 95169084 + ... + 95175876.

It is an arithmetic number, because the mean of its divisors is an integer number (3310750170).

Almost surely, 2^646506656640 is an apocalyptic number.

646506656640 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 646506656640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1271328065280).

646506656640 is an abundant number, since it is smaller than the sum of its proper divisors (1896149473920).

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

646506656640 is a wasteful number, since it uses less digits than its factorization.

646506656640 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6903 (or 6888 counting only the distinct ones).

The product of its (nonzero) digits is 18662400, while the sum is 54.

The spelling of 646506656640 in words is "six hundred forty-six billion, five hundred six million, six hundred fifty-six thousand, six hundred forty".