1821553 has 2 divisors, whose sum is σ = 1821554. Its totient is φ = 1821552.

The previous prime is 1821551. The next prime is 1821571. The reversal of 1821553 is 3551281.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1420864 + 400689 = 1192^2 + 633^2 .

It is a cyclic number.

It is not a de Polignac number, because 1821553 - 2¹ = 1821551 is a prime.

Together with 1821551, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (1821551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 910776 + 910777.

It is an arithmetic number, because the mean of its divisors is an integer number (910777).

2^1821553 is an apocalyptic number.

It is an amenable number.

1821553 is a deficient number, since it is larger than the sum of its proper divisors (1).

1821553 is an equidigital number, since it uses as much as digits as its factorization.

1821553 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 1200, while the sum is 25.

The square root of 1821553 is about 1349.6492136848. The cubic root of 1821553 is about 122.1276322624.

The spelling of 1821553 in words is "one million, eight hundred twenty-one thousand, five hundred fifty-three".