11566781 has 2 divisors, whose sum is σ = 11566782. Its totient is φ = 11566780.

The previous prime is 11566771. The next prime is 11566811. The reversal of 11566781 is 18766511.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 8791225 + 2775556 = 2965^2 + 1666^2 .

It is a cyclic number.

It is not a de Polignac number, because 11566781 - 2⁶ = 11566717 is a prime.

It is a super-2 number, since 2×11566781² = 267580845403922, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Chen prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (11566741) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5783390 + 5783391.

It is an arithmetic number, because the mean of its divisors is an integer number (5783391).

Almost surely, 2^11566781 is an apocalyptic number.

It is an amenable number.

11566781 is a deficient number, since it is larger than the sum of its proper divisors (1).

11566781 is an equidigital number, since it uses as much as digits as its factorization.

11566781 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 10080, while the sum is 35.

The square root of 11566781 is about 3400.9970596871. The cubic root of 11566781 is about 226.1539465898.

The spelling of 11566781 in words is "eleven million, five hundred sixty-six thousand, seven hundred eighty-one".