721409 has 8 divisors (see below), whose sum is σ = 783552. Its totient is φ = 660240.

The previous prime is 721397. The next prime is 721439. The reversal of 721409 is 904127.

721409 is nontrivially palindromic in base 15.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-721409 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 (721439) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2612 + ... + 2874.

It is an arithmetic number, because the mean of its divisors is an integer number (97944).

2⁷²¹⁴⁰⁹ is an apocalyptic number.

It is an amenable number.

721409 is a deficient number, since it is larger than the sum of its proper divisors (62143).

721409 is a wasteful number, since it uses less digits than its factorization.

721409 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 487.

The product of its (nonzero) digits is 504, while the sum is 23.

The square root of 721409 is about 849.3579928393. The cubic root of 721409 is about 89.6865225686.

The spelling of 721409 in words is "seven hundred twenty-one thousand, four hundred nine".