115551781 has 2 divisors, whose sum is σ = 115551782. Its totient is φ = 115551780.

The previous prime is 115551767. The next prime is 115551811. The reversal of 115551781 is 187155511.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 83448225 + 32103556 = 9135^2 + 5666^2 .

It is an emirp because it is prime and its reverse (187155511) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 115551781 - 2⁹ = 115551269 is a prime.

It is a super-2 number, since 2×115551781² = 26704428184543922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (115551721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 57775890 + 57775891.

It is an arithmetic number, because the mean of its divisors is an integer number (57775891).

Almost surely, 2^115551781 is an apocalyptic number.

It is an amenable number.

115551781 is a deficient number, since it is larger than the sum of its proper divisors (1).

115551781 is an equidigital number, since it uses as much as digits as its factorization.

115551781 is an evil number, because the sum of its binary digits is even.

The product of its digits is 7000, while the sum is 34.

The square root of 115551781 is about 10749.5014302990. The cubic root of 115551781 is about 487.0709348583.

The spelling of 115551781 in words is "one hundred fifteen million, five hundred fifty-one thousand, seven hundred eighty-one".