409721 has 4 divisors (see below), whose sum is σ = 441252. Its totient is φ = 378192.

The previous prime is 409711. The next prime is 409723. The reversal of 409721 is 127904.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 55696 + 354025 = 236^2 + 595^2 .

It is a cyclic number.

It is not a de Polignac number, because 409721 - 2⁶ = 409657 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (409723) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 15746 + ... + 15771.

It is an arithmetic number, because the mean of its divisors is an integer number (110313).

2⁴⁰⁹⁷²¹ is an apocalyptic number.

It is an amenable number.

409721 is a deficient number, since it is larger than the sum of its proper divisors (31531).

409721 is a wasteful number, since it uses less digits than its factorization.

409721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 31530.

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

The square root of 409721 is about 640.0945242697. The cubic root of 409721 is about 74.2727335377.

The spelling of 409721 in words is "four hundred nine thousand, seven hundred twenty-one".