7181721121 has 4 divisors (see below), whose sum is σ = 7183212544. Its totient is φ = 7180229700.

The previous prime is 7181721109. The next prime is 7181721139. The reversal of 7181721121 is 1211271817.

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 a de Polignac number, because none of the positive numbers 2^k-7181721121 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (7181721221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 738465 + ... + 748126.

It is an arithmetic number, because the mean of its divisors is an integer number (1795803136).

Almost surely, 2^7181721121 is an apocalyptic number.

It is an amenable number.

7181721121 is a deficient number, since it is larger than the sum of its proper divisors (1491423).

7181721121 is a wasteful number, since it uses less digits than its factorization.

7181721121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1491422.

The product of its digits is 1568, while the sum is 31.

The square root of 7181721121 is about 84745.0359667161. The cubic root of 7181721121 is about 1929.3433044602.

Adding to 7181721121 its reverse (1211271817), we get a palindrome (8392992938).

The spelling of 7181721121 in words is "seven billion, one hundred eighty-one million, seven hundred twenty-one thousand, one hundred twenty-one".