115551721 has 2 divisors, whose sum is σ = 115551722. Its totient is φ = 115551720.

The previous prime is 115551697. The next prime is 115551731. The reversal of 115551721 is 127155511.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 112593321 + 2958400 = 10611^2 + 1720^2 .

It is a cyclic number.

It is not a de Polignac number, because 115551721 - 2¹¹ = 115549673 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 115551721.

It is not a weakly prime, because it can be changed into another prime (115551731) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 57775860 + 57775861.

It is an arithmetic number, because the mean of its divisors is an integer number (57775861).

Almost surely, 2^115551721 is an apocalyptic number.

It is an amenable number.

115551721 is a deficient number, since it is larger than the sum of its proper divisors (1).

115551721 is an equidigital number, since it uses as much as digits as its factorization.

115551721 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1750, while the sum is 28.

The square root of 115551721 is about 10749.4986394715. The cubic root of 115551721 is about 487.0708505548.

The spelling of 115551721 in words is "one hundred fifteen million, five hundred fifty-one thousand, seven hundred twenty-one".