1801781 has 2 divisors, whose sum is σ = 1801782. Its totient is φ = 1801780.

The previous prime is 1801777. The next prime is 1801817. The reversal of 1801781 is 1871081.

Together with next prime (1801817) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1359556 + 442225 = 1166^2 + 665^2 .

It is an emirp because it is prime and its reverse (1871081) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1801781 - 2² = 1801777 is a prime.

It is a super-2 number, since 2×1801781² = 6492829543922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1801781.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1801771) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 900890 + 900891.

It is an arithmetic number, because the mean of its divisors is an integer number (900891).

2^1801781 is an apocalyptic number.

It is an amenable number.

1801781 is a deficient number, since it is larger than the sum of its proper divisors (1).

1801781 is an equidigital number, since it uses as much as digits as its factorization.

1801781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 448, while the sum is 26.

The square root of 1801781 is about 1342.3043619090. The cubic root of 1801781 is about 121.6841466931.

The spelling of 1801781 in words is "one million, eight hundred one thousand, seven hundred eighty-one".