185821 has 2 divisors, whose sum is σ = 185822. Its totient is φ = 185820.

The previous prime is 185819. The next prime is 185831. The reversal of 185821 is 128581.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 168921 + 16900 = 411^2 + 130^2 .

It is a cyclic number.

It is not a de Polignac number, because 185821 - 2¹ = 185819 is a prime.

Together with 185819, it forms a pair of twin primes.

It is equal to p₁₆₈₁₉ and since 185821 and 16819 have the same sum of digits, it is a Honaker prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (185831) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 92910 + 92911.

It is an arithmetic number, because the mean of its divisors is an integer number (92911).

2¹⁸⁵⁸²¹ is an apocalyptic number.

It is an amenable number.

185821 is a deficient number, since it is larger than the sum of its proper divisors (1).

185821 is an equidigital number, since it uses as much as digits as its factorization.

185821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 640, while the sum is 25.

The square root of 185821 is about 431.0695999488. The cubic root of 185821 is about 57.0643573893.

The spelling of 185821 in words is "one hundred eighty-five thousand, eight hundred twenty-one".