11551781 has 2 divisors, whose sum is σ = 11551782. Its totient is φ = 11551780.

The previous prime is 11551769. The next prime is 11551783. The reversal of 11551781 is 18715511.

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., 11498881 + 52900 = 3391^2 + 230^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-11551781 is a prime.

It is a super-2 number, since 2×11551781² = 266887288543922, which contains 22 as substring.

Together with 11551783, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (11551783) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5775890 + 5775891.

It is an arithmetic number, because the mean of its divisors is an integer number (5775891).

Almost surely, 2^11551781 is an apocalyptic number.

It is an amenable number.

11551781 is a deficient number, since it is larger than the sum of its proper divisors (1).

11551781 is an equidigital number, since it uses as much as digits as its factorization.

11551781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1400, while the sum is 29.

The square root of 11551781 is about 3398.7911086149. The cubic root of 11551781 is about 226.0561441946.

The spelling of 11551781 in words is "eleven million, five hundred fifty-one thousand, seven hundred eighty-one".