721138331 has 16 divisors (see below), whose sum is σ = 786739200. Its totient is φ = 658391328.

The previous prime is 721138303. The next prime is 721138357. The reversal of 721138331 is 133831127.

It is a cyclic number.

It is not a de Polignac number, because 721138331 - 2²² = 716944027 is a prime.

It is a super-2 number, since 2×721138331² = 1040080984874931122, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (29).

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 721138294 and 721138303.

It is not an unprimeable number, because it can be changed into a prime (721138361) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 432806 + ... + 434468.

It is an arithmetic number, because the mean of its divisors is an integer number (49171200).

Almost surely, 2^721138331 is an apocalyptic number.

721138331 is a deficient number, since it is larger than the sum of its proper divisors (65600869).

721138331 is a wasteful number, since it uses less digits than its factorization.

721138331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2498.

The product of its digits is 3024, while the sum is 29.

The square root of 721138331 is about 26854.0188984815. The cubic root of 721138331 is about 896.7530452265.

Adding to 721138331 its reverse (133831127), we get a palindrome (854969458).

The spelling of 721138331 in words is "seven hundred twenty-one million, one hundred thirty-eight thousand, three hundred thirty-one".