1820261 has 2 divisors, whose sum is σ = 1820262. Its totient is φ = 1820260.

The previous prime is 1820249. The next prime is 1820267. The reversal of 1820261 is 1620281.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1809025 + 11236 = 1345^2 + 106^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-1820261 is a prime.

It is a Sophie Germain prime.

It is a Chen prime.

It is an Ulam number.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1820267) by changing a digit.

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 910130 + 910131.

It is an arithmetic number, because the mean of its divisors is an integer number (910131).

2^1820261 is an apocalyptic number.

It is an amenable number.

1820261 is a deficient number, since it is larger than the sum of its proper divisors (1).

1820261 is an equidigital number, since it uses as much as digits as its factorization.

1820261 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 1820261 is about 1349.1704858912. The cubic root of 1820261 is about 122.0987510054.

Adding to 1820261 its sum of digits (20), we get a palindrome (1820281).

The spelling of 1820261 in words is "one million, eight hundred twenty thousand, two hundred sixty-one".