1155821 has 2 divisors, whose sum is σ = 1155822. Its totient is φ = 1155820.

The previous prime is 1155733. The next prime is 1155823. The reversal of 1155821 is 1285511.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1155625 + 196 = 1075^2 + 14^2 .

It is an emirp because it is prime and its reverse (1285511) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1155821 is a prime.

Together with 1155823, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1155823) by changing a digit.

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

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 577910 + 577911.

It is an arithmetic number, because the mean of its divisors is an integer number (577911).

2^1155821 is an apocalyptic number.

It is an amenable number.

1155821 is a deficient number, since it is larger than the sum of its proper divisors (1).

1155821 is an equidigital number, since it uses as much as digits as its factorization.

1155821 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 400, while the sum is 23.

The square root of 1155821 is about 1075.0911589256. The cubic root of 1155821 is about 104.9454289370.

The spelling of 1155821 in words is "one million, one hundred fifty-five thousand, eight hundred twenty-one".