821680 has 20 divisors (see below), whose sum is σ = 1910592. Its totient is φ = 328640.

The previous prime is 821677. The next prime is 821741. The reversal of 821680 is 86128.

It is a tau number, because it is divible by the number of its divisors (20).

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 5056 + ... + 5215.

2⁸²¹⁶⁸⁰ is an apocalyptic number.

821680 is a gapful number since it is divisible by the number (80) formed by its first and last digit.

It is an amenable number.

821680 is an abundant number, since it is smaller than the sum of its proper divisors (1088912).

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

821680 is a wasteful number, since it uses less digits than its factorization.

821680 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 10284 (or 10278 counting only the distinct ones).

The product of its (nonzero) digits is 768, while the sum is 25.

The square root of 821680 is about 906.4656639940. The cubic root of 821680 is about 93.6628939069.

The spelling of 821680 in words is "eight hundred twenty-one thousand, six hundred eighty".