821101 has 2 divisors, whose sum is σ = 821102. Its totient is φ = 821100.

The previous prime is 821099. The next prime is 821113. The reversal of 821101 is 101128.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 561001 + 260100 = 749^2 + 510^2 .

It is a cyclic number.

It is not a de Polignac number, because 821101 - 2¹ = 821099 is a prime.

Together with 821099, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (821131) 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 as a sum of consecutive naturals, namely, 410550 + 410551.

It is an arithmetic number, because the mean of its divisors is an integer number (410551).

2⁸²¹¹⁰¹ is an apocalyptic number.

It is an amenable number.

821101 is a deficient number, since it is larger than the sum of its proper divisors (1).

821101 is an equidigital number, since it uses as much as digits as its factorization.

821101 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 16, while the sum is 13.

The square root of 821101 is about 906.1462354389. The cubic root of 821101 is about 93.6408887635.

Adding to 821101 its reverse (101128), we get a palindrome (922229).

The spelling of 821101 in words is "eight hundred twenty-one thousand, one hundred one".