2181549115973 has 4 divisors (see below), whose sum is σ = 2181552742188. Its totient is φ = 2181545489760.

The previous prime is 2181549115969. The next prime is 2181549116093. The reversal of 2181549115973 is 3795119451812.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 1126998806404 + 1054550309569 = 1061602^2 + 1026913^2 .

It is a cyclic number.

It is not a de Polignac number, because 2181549115973 - 2² = 2181549115969 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2181549115073) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 670808 + ... + 2193873.

It is an arithmetic number, because the mean of its divisors is an integer number (545388185547).

Almost surely, 2^{2181549115973} is an apocalyptic number.

It is an amenable number.

2181549115973 is a deficient number, since it is larger than the sum of its proper divisors (3626215).

2181549115973 is an equidigital number, since it uses as much as digits as its factorization.

2181549115973 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3626214.

The product of its digits is 2721600, while the sum is 56.

The spelling of 2181549115973 in words is "two trillion, one hundred eighty-one billion, five hundred forty-nine million, one hundred fifteen thousand, nine hundred seventy-three".