1821821 has 2 divisors, whose sum is σ = 1821822. Its totient is φ = 1821820.

The previous prime is 1821791. The next prime is 1821847. The reversal of 1821821 is 1281281.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1792921 + 28900 = 1339^2 + 170^2 .

It is an emirp because it is prime and its reverse (1281281) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1821821 is a prime.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1821871) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 910910 + 910911.

It is an arithmetic number, because the mean of its divisors is an integer number (910911).

2^1821821 is an apocalyptic number.

It is an amenable number.

1821821 is a deficient number, since it is larger than the sum of its proper divisors (1).

1821821 is an equidigital number, since it uses as much as digits as its factorization.

1821821 is an evil number, because the sum of its binary digits is even.

The product of its digits is 256, while the sum is 23.

The square root of 1821821 is about 1349.7484950908. The cubic root of 1821821 is about 122.1336214011.

The spelling of 1821821 in words is "one million, eight hundred twenty-one thousand, eight hundred twenty-one".