821240 has 48 divisors (see below), whose sum is σ = 2154600. Its totient is φ = 280896.

The previous prime is 821209. The next prime is 821263. The reversal of 821240 is 42128.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1751 + ... + 2169.

2⁸²¹²⁴⁰ 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 821240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1077300).

821240 is an abundant number, since it is smaller than the sum of its proper divisors (1333360).

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

821240 is a wasteful number, since it uses less digits than its factorization.

821240 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 444 (or 433 counting only the distinct ones).

The product of its (nonzero) digits is 128, while the sum is 17.

The square root of 821240 is about 906.2229306302. Note that the first 3 decimals coincide. The cubic root of 821240 is about 93.6461724615.

Adding to 821240 its reverse (42128), we get a palindrome (863368).

The spelling of 821240 in words is "eight hundred twenty-one thousand, two hundred forty".