2161721115 has 40 divisors (see below), whose sum is σ = 3979844880. Its totient is φ = 1121750208.

The previous prime is 2161721101. The next prime is 2161721117. The reversal of 2161721115 is 5111271612.

2161721115 is a `hidden beast` number, since 21 + 617 + 2 + 11 + 15 = 666.

2161721115 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 2161721115 - 2⁵ = 2161721083 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (2161721117) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 57145 + ... + 87114.

It is an arithmetic number, because the mean of its divisors is an integer number (99496122).

Almost surely, 2^2161721115 is an apocalyptic number.

2161721115 is a deficient number, since it is larger than the sum of its proper divisors (1818123765).

2161721115 is a wasteful number, since it uses less digits than its factorization.

2161721115 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 144313 (or 144304 counting only the distinct ones).

The product of its digits is 840, while the sum is 27.

The square root of 2161721115 is about 46494.3127167184. The cubic root of 2161721115 is about 1293.0040589663.

Adding to 2161721115 its reverse (5111271612), we get a palindrome (7272992727).

The spelling of 2161721115 in words is "two billion, one hundred sixty-one million, seven hundred twenty-one thousand, one hundred fifteen".