721209 has 8 divisors (see below), whose sum is σ = 965952. Its totient is φ = 478640.

The previous prime is 721207. The next prime is 721213. The reversal of 721209 is 902127.

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 721209 - 2¹ = 721207 is a prime.

It is not an unprimeable number, because it can be changed into a prime (721207) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 547 + ... + 1319.

It is an arithmetic number, because the mean of its divisors is an integer number (120744).

2⁷²¹²⁰⁹ is an apocalyptic number.

It is an amenable number.

721209 is a deficient number, since it is larger than the sum of its proper divisors (244743).

721209 is a wasteful number, since it uses less digits than its factorization.

721209 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1087.

The product of its (nonzero) digits is 252, while the sum is 21.

The square root of 721209 is about 849.2402486929. The cubic root of 721209 is about 89.6782337143.

The spelling of 721209 in words is "seven hundred twenty-one thousand, two hundred nine".