821681280 has 256 divisors, whose sum is σ = 3326342400. Its totient is φ = 187785216.

The previous prime is 821681269. The next prime is 821681297. The reversal of 821681280 is 82186128.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 117564 + ... + 124356.

It is an arithmetic number, because the mean of its divisors is an integer number (12993525).

Almost surely, 2^821681280 is an apocalyptic number.

821681280 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 821681280, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1663171200).

821681280 is an abundant number, since it is smaller than the sum of its proper divisors (2504661120).

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

821681280 is a wasteful number, since it uses less digits than its factorization.

821681280 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6828 (or 6810 counting only the distinct ones).

The product of its (nonzero) digits is 12288, while the sum is 36.

The square root of 821681280 is about 28664.9835164788. The cubic root of 821681280 is about 936.6294254235.

The spelling of 821681280 in words is "eight hundred twenty-one million, six hundred eighty-one thousand, two hundred eighty".