821660 has 24 divisors (see below), whose sum is σ = 1972320. Its totient is φ = 281664.

The previous prime is 821651. The next prime is 821663. The reversal of 821660 is 66128.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821663) by changing a digit.

821660 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 7 ways as a sum of consecutive naturals, for example, 2795 + ... + 3074.

It is an arithmetic number, because the mean of its divisors is an integer number (82180).

2⁸²¹⁶⁶⁰ is an apocalyptic number.

It is an amenable number.

821660 is an abundant number, since it is smaller than the sum of its proper divisors (1150660).

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

821660 is a wasteful number, since it uses less digits than its factorization.

821660 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5885 (or 5883 counting only the distinct ones).

The product of its (nonzero) digits is 576, while the sum is 23.

The square root of 821660 is about 906.4546320694. The cubic root of 821660 is about 93.6621339707.

Adding to 821660 its reverse (66128), we get a palindrome (887788).

The spelling of 821660 in words is "eight hundred twenty-one thousand, six hundred sixty".