821228647680 has 864 divisors, whose sum is σ = 3432437527680. Its totient is φ = 187678052352.

The previous prime is 821228647651. The next prime is 821228647711. The reversal of 821228647680 is 86746822128.

821228647680 is a `hidden beast` number, since 8 + 2 + 12 + 2 + 86 + 476 + 80 = 666.

It is a tau number, because it is divible by the number of its divisors (864).

It is a Harshad number since it is a multiple of its sum of digits (54).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 137165647 + ... + 137171633.

It is an arithmetic number, because the mean of its divisors is an integer number (3972728620).

Almost surely, 2^821228647680 is an apocalyptic number.

821228647680 is a gapful number since it is divisible by the number (80) 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 821228647680, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1716218763840).

821228647680 is an abundant number, since it is smaller than the sum of its proper divisors (2611208880000).

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

821228647680 is an frugal number, since it uses more digits than its factorization.

821228647680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6043 (or 6004 counting only the distinct ones).

The product of its (nonzero) digits is 4128768, while the sum is 54.

The spelling of 821228647680 in words is "eight hundred twenty-one billion, two hundred twenty-eight million, six hundred forty-seven thousand, six hundred eighty".