721739 has 2 divisors, whose sum is σ = 721740. Its totient is φ = 721738.

The previous prime is 721733. The next prime is 721783. The reversal of 721739 is 937127.

It is a happy number.

It is a weak prime.

It is an emirp because it is prime and its reverse (937127) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-721739 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (721733) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 360869 + 360870.

It is an arithmetic number, because the mean of its divisors is an integer number (360870).

2⁷²¹⁷³⁹ is an apocalyptic number.

721739 is a deficient number, since it is larger than the sum of its proper divisors (1).

721739 is an equidigital number, since it uses as much as digits as its factorization.

721739 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 2646, while the sum is 29.

The square root of 721739 is about 849.5522350038. The cubic root of 721739 is about 89.7001958297.

The spelling of 721739 in words is "seven hundred twenty-one thousand, seven hundred thirty-nine".