1821997 has 2 divisors, whose sum is σ = 1821998. Its totient is φ = 1821996.

The previous prime is 1821959. The next prime is 1822003. The reversal of 1821997 is 7991281.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1798281 + 23716 = 1341^2 + 154^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1821997 is a prime.

1821997 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1821497) by changing a digit.

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

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 910998 + 910999.

It is an arithmetic number, because the mean of its divisors is an integer number (910999).

2^1821997 is an apocalyptic number.

It is an amenable number.

1821997 is a deficient number, since it is larger than the sum of its proper divisors (1).

1821997 is an equidigital number, since it uses as much as digits as its factorization.

1821997 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 9072, while the sum is 37.

The square root of 1821997 is about 1349.8136908477. The cubic root of 1821997 is about 122.1375542473.

The spelling of 1821997 in words is "one million, eight hundred twenty-one thousand, nine hundred ninety-seven".