819840 has 128 divisors (see below), whose sum is σ = 3035520. Its totient is φ = 184320.

The previous prime is 819829. The next prime is 819853. The reversal of 819840 is 48918.

It is a happy number.

819840 is a nontrivial binomial coefficient, being equal to C(1281, 2).

It is a tau number, because it is divible by the number of its divisors (128).

It is a Harshad number since it is a multiple of its sum of digits (30).

It is a junction number, because it is equal to n+sod(n) for n = 819798 and 819807.

It is an unprimeable number.

819840 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 13410 + ... + 13470.

It is an arithmetic number, because the mean of its divisors is an integer number (23715).

2⁸¹⁹⁸⁴⁰ is an apocalyptic number.

819840 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

819840 is the 1280-th triangular number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 819840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1517760).

819840 is an abundant number, since it is smaller than the sum of its proper divisors (2215680).

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

819840 is a wasteful number, since it uses less digits than its factorization.

819840 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90 (or 78 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 30.

The square root of 819840 is about 905.4501642829. The cubic root of 819840 is about 93.5929280945.

The spelling of 819840 in words is "eight hundred nineteen thousand, eight hundred forty".