721231121 has 32 divisors (see below), whose sum is σ = 829613568. Its totient is φ = 622391040.

The previous prime is 721231087. The next prime is 721231129. The reversal of 721231121 is 121132127.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-721231121 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 721231093 and 721231102.

It is not an unprimeable number, because it can be changed into a prime (721231129) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1378766 + ... + 1379288.

It is an arithmetic number, because the mean of its divisors is an integer number (25925424).

Almost surely, 2^721231121 is an apocalyptic number.

It is an amenable number.

721231121 is a deficient number, since it is larger than the sum of its proper divisors (108382447).

721231121 is a wasteful number, since it uses less digits than its factorization.

721231121 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 681.

The product of its digits is 168, while the sum is 20.

The square root of 721231121 is about 26855.7465172726. The cubic root of 721231121 is about 896.7915057839.

Adding to 721231121 its reverse (121132127), we get a palindrome (842363248).

The spelling of 721231121 in words is "seven hundred twenty-one million, two hundred thirty-one thousand, one hundred twenty-one".