821620 has 12 divisors (see below), whose sum is σ = 1725444. Its totient is φ = 328640.

The previous prime is 821603. The next prime is 821641. The reversal of 821620 is 26128.

821620 = 227² + 228² + ... + 241².

It is a happy number.

It can be written as a sum of positive squares in 2 ways, for example, as 320356 + 501264 = 566^2 + 708^2 .

It is a plaindrome in base 15.

It is a congruent number.

It is an unprimeable number.

821620 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 3 ways as a sum of consecutive naturals, for example, 20521 + ... + 20560.

It is an arithmetic number, because the mean of its divisors is an integer number (143787).

2⁸²¹⁶²⁰ is an apocalyptic number.

It is an amenable number.

821620 is an abundant number, since it is smaller than the sum of its proper divisors (903824).

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

821620 is a wasteful number, since it uses less digits than its factorization.

821620 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41090 (or 41088 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 19.

The square root of 821620 is about 906.4325678174. The cubic root of 821620 is about 93.6606140613.

Adding to 821620 its reverse (26128), we get a palindrome (847748).

It can be divided in two parts, 821 and 620, that added together give a palindrome (1441).

The spelling of 821620 in words is "eight hundred twenty-one thousand, six hundred twenty".