721136 has 20 divisors (see below), whose sum is σ = 1505112. Its totient is φ = 332736.

The previous prime is 721129. The next prime is 721139. The reversal of 721136 is 631127.

It is a happy number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 721136.

It is not an unprimeable number, because it can be changed into a prime (721139) by changing a digit.

721136 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1526 + ... + 1941.

2⁷²¹¹³⁶ is an apocalyptic number.

It is an amenable number.

721136 is an abundant number, since it is smaller than the sum of its proper divisors (783976).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

721136 is a wasteful number, since it uses less digits than its factorization.

721136 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3488 (or 3482 counting only the distinct ones).

The product of its digits is 252, while the sum is 20.

The square root of 721136 is about 849.1972680126. The cubic root of 721136 is about 89.6752079007.

Subtracting from 721136 its reverse (631127), we obtain a palindrome (90009).

The spelling of 721136 in words is "seven hundred twenty-one thousand, one hundred thirty-six".