823440 has 80 divisors (see below), whose sum is σ = 2642688. Its totient is φ = 211968.

The previous prime is 823421. The next prime is 823447. The reversal of 823440 is 44328.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (80).

It is not an unprimeable number, because it can be changed into a prime (823447) by changing a digit.

823440 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 11244 + ... + 11316.

2⁸²³⁴⁴⁰ is an apocalyptic number.

823440 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 823440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1321344).

823440 is an abundant number, since it is smaller than the sum of its proper divisors (1819248).

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

823440 is a wasteful number, since it uses less digits than its factorization.

823440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 136 (or 130 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 21.

The square root of 823440 is about 907.4359481528. The cubic root of 823440 is about 93.7297200578.

Adding to 823440 its reverse (44328), we get a palindrome (867768).

The spelling of 823440 in words is "eight hundred twenty-three thousand, four hundred forty".