721789 has 4 divisors (see below), whose sum is σ = 725760. Its totient is φ = 717820.

The previous prime is 721783. The next prime is 721793. The reversal of 721789 is 987127.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 721789 - 2⁷ = 721661 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721783) 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 3 ways as a sum of consecutive naturals, for example, 1699 + ... + 2080.

It is an arithmetic number, because the mean of its divisors is an integer number (181440).

2⁷²¹⁷⁸⁹ is an apocalyptic number.

It is an amenable number.

721789 is a deficient number, since it is larger than the sum of its proper divisors (3971).

721789 is a wasteful number, since it uses less digits than its factorization.

721789 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3970.

The product of its digits is 7056, while the sum is 34.

The square root of 721789 is about 849.5816617607. The cubic root of 721789 is about 89.7022671723.

The spelling of 721789 in words is "seven hundred twenty-one thousand, seven hundred eighty-nine".