2211081721 has 4 divisors (see below), whose sum is σ = 2211193600. Its totient is φ = 2210969844.

The previous prime is 2211081707. The next prime is 2211081731. The reversal of 2211081721 is 1271801122.

It is a happy number.

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, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 2211081721 - 2¹⁷ = 2210950649 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (2211081731) 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, 17481 + ... + 68758.

It is an arithmetic number, because the mean of its divisors is an integer number (552798400).

Almost surely, 2^2211081721 is an apocalyptic number.

It is an amenable number.

2211081721 is a deficient number, since it is larger than the sum of its proper divisors (111879).

2211081721 is an equidigital number, since it uses as much as digits as its factorization.

2211081721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 111878.

The product of its (nonzero) digits is 448, while the sum is 25.

The square root of 2211081721 is about 47022.1407530538. The cubic root of 2211081721 is about 1302.7715467401.

Adding to 2211081721 its reverse (1271801122), we get a palindrome (3482882843).

The spelling of 2211081721 in words is "two billion, two hundred eleven million, eighty-one thousand, seven hundred twenty-one".