821819 has 2 divisors, whose sum is σ = 821820. Its totient is φ = 821818.

The previous prime is 821809. The next prime is 821827. The reversal of 821819 is 918128.

821819 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 821819 - 2⁴ = 821803 is a prime.

It is a super-2 number, since 2×821819² = 1350772937522, which contains 22 as substring.

It is a Sophie Germain prime.

It is equal to p₆₅₅₄₉ and since 821819 and 65549 have the same sum of digits, it is a Honaker prime.

It is a plaindrome in base 15.

It is a junction number, because it is equal to n+sod(n) for n = 821791 and 821800.

It is not a weakly prime, because it can be changed into another prime (821809) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 410909 + 410910.

It is an arithmetic number, because the mean of its divisors is an integer number (410910).

2⁸²¹⁸¹⁹ is an apocalyptic number.

821819 is a deficient number, since it is larger than the sum of its proper divisors (1).

821819 is an equidigital number, since it uses as much as digits as its factorization.

821819 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1152, while the sum is 29.

The square root of 821819 is about 906.5423321611. The cubic root of 821819 is about 93.6681751227.

The spelling of 821819 in words is "eight hundred twenty-one thousand, eight hundred nineteen".