821871 has 12 divisors (see below), whose sum is σ = 1210248. Its totient is φ = 537264.

The previous prime is 821869. The next prime is 821879. The reversal of 821871 is 178128.

It is not a de Polignac number, because 821871 - 2¹ = 821869 is a prime.

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (821879) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 385 + ... + 1338.

It is an arithmetic number, because the mean of its divisors is an integer number (100854).

2⁸²¹⁸⁷¹ is an apocalyptic number.

821871 is a deficient number, since it is larger than the sum of its proper divisors (388377).

821871 is a wasteful number, since it uses less digits than its factorization.

821871 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1782 (or 1779 counting only the distinct ones).

The product of its digits is 896, while the sum is 27.

The square root of 821871 is about 906.5710121110. The cubic root of 821871 is about 93.6701506762.

Adding to 821871 its reverse (178128), we get a palindrome (999999).

It can be divided in two parts, 82 and 1871, that added together give a triangular number (1953 = T₆₂).

The spelling of 821871 in words is "eight hundred twenty-one thousand, eight hundred seventy-one".