721331 has 4 divisors (see below), whose sum is σ = 776832. Its totient is φ = 665832.

The previous prime is 721321. The next prime is 721333. The reversal of 721331 is 133127.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 721331 - 2⁶ = 721267 is a prime.

It is a super-2 number, since 2×721331² = 1040636823122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (721333) 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, 27731 + ... + 27756.

It is an arithmetic number, because the mean of its divisors is an integer number (194208).

2⁷²¹³³¹ is an apocalyptic number.

721331 is a deficient number, since it is larger than the sum of its proper divisors (55501).

721331 is a wasteful number, since it uses less digits than its factorization.

721331 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55500.

The product of its digits is 126, while the sum is 17.

The square root of 721331 is about 849.3120745639. The cubic root of 721331 is about 89.6832900977.

Adding to 721331 its reverse (133127), we get a palindrome (854458).

The spelling of 721331 in words is "seven hundred twenty-one thousand, three hundred thirty-one".