1821331378944 has 648 divisors, whose sum is σ = 6649217422848. Its totient is φ = 465808527360.

The previous prime is 1821331378931. The next prime is 1821331378991. The reversal of 1821331378944 is 4498731331281.

1821331378944 is a `hidden beast` number, since 1 + 8 + 213 + 313 + 78 + 9 + 44 = 666.

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 796383369 + ... + 796385655.

Almost surely, 2^{1821331378944} is an apocalyptic number.

1821331378944 is a gapful number since it is divisible by the number (14) 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 1821331378944, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3324608711424).

1821331378944 is an abundant number, since it is smaller than the sum of its proper divisors (4827886043904).

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

1821331378944 is a wasteful number, since it uses less digits than its factorization.

1821331378944 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2461 (or 2377 counting only the distinct ones).

The product of its digits is 3483648, while the sum is 54.

The spelling of 1821331378944 in words is "one trillion, eight hundred twenty-one billion, three hundred thirty-one million, three hundred seventy-eight thousand, nine hundred forty-four".