721839 has 8 divisors (see below), whose sum is σ = 995760. Its totient is φ = 464576.

The previous prime is 721793. The next prime is 721843. The reversal of 721839 is 938127.

It is a happy number.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 721839 - 2¹¹ = 719791 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721849) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 4062 + ... + 4235.

It is an arithmetic number, because the mean of its divisors is an integer number (124470).

2⁷²¹⁸³⁹ is an apocalyptic number.

721839 is a deficient number, since it is larger than the sum of its proper divisors (273921).

721839 is a wasteful number, since it uses less digits than its factorization.

721839 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8329.

The product of its digits is 3024, while the sum is 30.

The square root of 721839 is about 849.6110874983. The cubic root of 721839 is about 89.7043384192.

The spelling of 721839 in words is "seven hundred twenty-one thousand, eight hundred thirty-nine".