819979021800 has 240 divisors, whose sum is σ = 2852306687340. Its totient is φ = 218323399680.

The previous prime is 819979021777. The next prime is 819979021801. The reversal of 819979021800 is 8120979918.

It can be written as a sum of positive squares in 6 ways, for example, as 417411613476 + 402567408324 = 646074^2 + 634482^2 .

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

It is not an unprimeable number, because it can be changed into a prime (819979021801) by changing a digit.

It is a polite number, since it can be written in 59 ways as a sum of consecutive naturals, for example, 10539844 + ... + 10617356.

Almost surely, 2^819979021800 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 819979021800, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1426153343670).

819979021800 is an abundant number, since it is smaller than the sum of its proper divisors (2032327665540).

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

819979021800 is a wasteful number, since it uses less digits than its factorization.

819979021800 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 78194 (or 78176 counting only the distinct ones).

The product of its (nonzero) digits is 653184, while the sum is 54.

The spelling of 819979021800 in words is "eight hundred nineteen billion, nine hundred seventy-nine million, twenty-one thousand, eight hundred".