821721120 has 192 divisors, whose sum is σ = 2972712960. Its totient is φ = 188697600.

The previous prime is 821721083. The next prime is 821721133. The reversal of 821721120 is 21127128.

It is a Harshad number since it is a multiple of its sum of digits (24).

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 96225 + ... + 104415.

It is an arithmetic number, because the mean of its divisors is an integer number (15482880).

Almost surely, 2^821721120 is an apocalyptic number.

821721120 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 821721120, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1486356480).

821721120 is an abundant number, since it is smaller than the sum of its proper divisors (2150991840).

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

821721120 is a wasteful number, since it uses less digits than its factorization.

821721120 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8239 (or 8231 counting only the distinct ones).

The product of its (nonzero) digits is 448, while the sum is 24.

The square root of 821721120 is about 28665.6784325786. The cubic root of 821721120 is about 936.6445629690.

Adding to 821721120 its reverse (21127128), we get a palindrome (842848248).

The spelling of 821721120 in words is "eight hundred twenty-one million, seven hundred twenty-one thousand, one hundred twenty".