821671 has 4 divisors (see below), whose sum is σ = 826000. Its totient is φ = 817344.

The previous prime is 821663. The next prime is 821677. The reversal of 821671 is 176128.

821671 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 821671 - 2³ = 821663 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821677) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1866 + ... + 2263.

It is an arithmetic number, because the mean of its divisors is an integer number (206500).

2⁸²¹⁶⁷¹ is an apocalyptic number.

821671 is a deficient number, since it is larger than the sum of its proper divisors (4329).

821671 is a wasteful number, since it uses less digits than its factorization.

821671 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4328.

The product of its digits is 672, while the sum is 25.

The square root of 821671 is about 906.4606996445. The cubic root of 821671 is about 93.6625519371.

Adding to 821671 its reverse (176128), we get a palindrome (997799).

The spelling of 821671 in words is "eight hundred twenty-one thousand, six hundred seventy-one".