821040 has 80 divisors (see below), whose sum is σ = 2785536. Its totient is φ = 198400.

The previous prime is 821039. The next prime is 821053. The reversal of 821040 is 40128.

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

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a nialpdrome in base 16.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 2485 + ... + 2795.

2⁸²¹⁰⁴⁰ is an apocalyptic number.

821040 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 821040, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1392768).

821040 is an abundant number, since it is smaller than the sum of its proper divisors (1964496).

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

821040 is a wasteful number, since it uses less digits than its factorization.

821040 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 338 (or 332 counting only the distinct ones).

The product of its (nonzero) digits is 64, while the sum is 15.

The square root of 821040 is about 906.1125757874. The cubic root of 821040 is about 93.6385698301.

Adding to 821040 its reverse (40128), we get a palindrome (861168).

The spelling of 821040 in words is "eight hundred twenty-one thousand, forty".