115661721 has 32 divisors (see below), whose sum is σ = 186485760. Its totient is φ = 62289216.

The previous prime is 115661719. The next prime is 115661723. The reversal of 115661721 is 127166511.

It is an interprime number because it is at equal distance from previous prime (115661719) and next prime (115661723).

It is not a de Polignac number, because 115661721 - 2¹ = 115661719 is a prime.

It is not an unprimeable number, because it can be changed into a prime (115661723) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 89935 + ... + 91211.

It is an arithmetic number, because the mean of its divisors is an integer number (5827680).

Almost surely, 2^115661721 is an apocalyptic number.

It is an amenable number.

115661721 is a deficient number, since it is larger than the sum of its proper divisors (70824039).

115661721 is a wasteful number, since it uses less digits than its factorization.

115661721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1533.

The product of its digits is 2520, while the sum is 30.

The square root of 115661721 is about 10754.6139400724. The cubic root of 115661721 is about 487.2253579935.

The spelling of 115661721 in words is "one hundred fifteen million, six hundred sixty-one thousand, seven hundred twenty-one".