1821391318656 has 640 divisors, whose sum is σ = 6711362380800. Its totient is φ = 480324888576.

The previous prime is 1821391318619. The next prime is 1821391318687. The reversal of 1821391318656 is 6568131931281.

1821391318656 is a `hidden beast` number, since 1 + 8 + 21 + 391 + 3 + 186 + 56 = 666.

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

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 159443761 + ... + 159455183.

It is an arithmetic number, because the mean of its divisors is an integer number (10486503720).

Almost surely, 2^{1821391318656} is an apocalyptic number.

1821391318656 is a gapful number since it is divisible by the number (16) 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 1821391318656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3355681190400).

1821391318656 is an abundant number, since it is smaller than the sum of its proper divisors (4889971062144).

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

1821391318656 is an equidigital number, since it uses as much as digits as its factorization.

1821391318656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11495 (or 11448 counting only the distinct ones).

The product of its digits is 1866240, while the sum is 54.

The spelling of 1821391318656 in words is "one trillion, eight hundred twenty-one billion, three hundred ninety-one million, three hundred eighteen thousand, six hundred fifty-six".