647656621920 has 864 divisors, whose sum is σ = 2852428400640. Its totient is φ = 132287662080.

The previous prime is 647656621919. The next prime is 647656622009. The reversal of 647656621920 is 29126656746.

647656621920 is a `hidden beast` number, since 6 + 4 + 7 + 6 + 5 + 6 + 621 + 9 + 2 + 0 = 666.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 45786369 + ... + 45800511.

It is an arithmetic number, because the mean of its divisors is an integer number (3301421760).

Almost surely, 2^647656621920 is an apocalyptic number.

647656621920 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 647656621920, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1426214200320).

647656621920 is an abundant number, since it is smaller than the sum of its proper divisors (2204771778720).

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

647656621920 is a wasteful number, since it uses less digits than its factorization.

647656621920 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 14248 (or 14230 counting only the distinct ones).

The product of its (nonzero) digits is 6531840, while the sum is 54.

The spelling of 647656621920 in words is "six hundred forty-seven billion, six hundred fifty-six million, six hundred twenty-one thousand, nine hundred twenty".