821520 has 120 divisors (see below), whose sum is σ = 3172416. Its totient is φ = 186624.

The previous prime is 821519. The next prime is 821551. The reversal of 821520 is 25128.

It is a tau number, because it is divible by the number of its divisors (120).

It is a super-2 number, since 2×821520² = 1349790220800, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is a junction number, because it is equal to n+sod(n) for n = 821493 and 821502.

It is an unprimeable number.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4959 + ... + 5121.

2⁸²¹⁵²⁰ is an apocalyptic number.

821520 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 821520, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1586208).

821520 is an abundant number, since it is smaller than the sum of its proper divisors (2350896).

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

821520 is a wasteful number, since it uses less digits than its factorization.

821520 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 189 (or 180 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 18.

The square root of 821520 is about 906.3774048375. The cubic root of 821520 is about 93.6568140721.

Adding to 821520 its reverse (25128), we get a palindrome (846648).

It can be divided in two parts, 8 and 21520, that added together give a triangular number (21528 = T₂₀₇).

The spelling of 821520 in words is "eight hundred twenty-one thousand, five hundred twenty".