2181717861 has 4 divisors (see below), whose sum is σ = 2908957152. Its totient is φ = 1454478572.

The previous prime is 2181717847. The next prime is 2181717869. The reversal of 2181717861 is 1687171812.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 2181717861 - 2⁵ = 2181717829 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (2181717869) 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, 363619641 + ... + 363619646.

It is an arithmetic number, because the mean of its divisors is an integer number (727239288).

Almost surely, 2^2181717861 is an apocalyptic number.

It is an amenable number.

2181717861 is a deficient number, since it is larger than the sum of its proper divisors (727239291).

2181717861 is an equidigital number, since it uses as much as digits as its factorization.

2181717861 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 727239290.

The product of its digits is 37632, while the sum is 42.

The square root of 2181717861 is about 46708.8627671452. The cubic root of 2181717861 is about 1296.9787553635.

The spelling of 2181717861 in words is "two billion, one hundred eighty-one million, seven hundred seventeen thousand, eight hundred sixty-one".