2181108721 has 12 divisors (see below), whose sum is σ = 2527592400. Its totient is φ = 1866186560.

The previous prime is 2181108697. The next prime is 2181108733. The reversal of 2181108721 is 1278011812.

It is not a de Polignac number, because 2181108721 - 2⁵ = 2181108689 is a prime.

It is a super-3 number, since 3×2181108721³ (a number of 29 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2181108751) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 339871 + ... + 346228.

It is an arithmetic number, because the mean of its divisors is an integer number (210632700).

Almost surely, 2^2181108721 is an apocalyptic number.

It is an amenable number.

2181108721 is a deficient number, since it is larger than the sum of its proper divisors (346483679).

2181108721 is a wasteful number, since it uses less digits than its factorization.

2181108721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 686144 (or 686127 counting only the distinct ones).

The product of its (nonzero) digits is 1792, while the sum is 31.

The square root of 2181108721 is about 46702.3417078844. The cubic root of 2181108721 is about 1296.8580377719.

The spelling of 2181108721 in words is "two billion, one hundred eighty-one million, one hundred eight thousand, seven hundred twenty-one".