821667 has 16 divisors (see below), whose sum is σ = 1366272. Its totient is φ = 426720.

The previous prime is 821663. The next prime is 821677. The reversal of 821667 is 766128.

It is a happy number.

It is not a de Polignac number, because 821667 - 2² = 821663 is a prime.

It is a plaindrome in base 15.

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

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1548 + ... + 2009.

It is an arithmetic number, because the mean of its divisors is an integer number (85392).

2⁸²¹⁶⁶⁷ is an apocalyptic number.

821667 is a deficient number, since it is larger than the sum of its proper divisors (544605).

821667 is a wasteful number, since it uses less digits than its factorization.

821667 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3578.

The product of its digits is 4032, while the sum is 30.

The square root of 821667 is about 906.4584932582. The cubic root of 821667 is about 93.6623999497.

The spelling of 821667 in words is "eight hundred twenty-one thousand, six hundred sixty-seven".