721205 has 4 divisors (see below), whose sum is σ = 865452. Its totient is φ = 576960.

The previous prime is 721199. The next prime is 721207. The reversal of 721205 is 502127.

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 358801 + 362404 = 599^2 + 602^2 .

It is not a de Polignac number, because 721205 - 2⁶ = 721141 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 (721207) 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, 72116 + ... + 72125.

It is an arithmetic number, because the mean of its divisors is an integer number (216363).

2⁷²¹²⁰⁵ is an apocalyptic number.

It is an amenable number.

721205 is a deficient number, since it is larger than the sum of its proper divisors (144247).

721205 is a wasteful number, since it uses less digits than its factorization.

721205 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 144246.

The product of its (nonzero) digits is 140, while the sum is 17.

The square root of 721205 is about 849.2378936435. The cubic root of 721205 is about 89.6780679216.

It can be divided in two parts, 7 and 21205, that added together give a palindrome (21212).

The spelling of 721205 in words is "seven hundred twenty-one thousand, two hundred five".