721445 has 4 divisors (see below), whose sum is σ = 865740. Its totient is φ = 577152.

The previous prime is 721439. The next prime is 721451. The reversal of 721445 is 544127.

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

It is an interprime number because it is at equal distance from previous prime (721439) and next prime (721451).

It can be written as a sum of positive squares in 2 ways, for example, as 134689 + 586756 = 367^2 + 766^2 .

It is a cyclic number.

It is not a de Polignac number, because 721445 - 2⁶ = 721381 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 721445.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 721445.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 72140 + ... + 72149.

It is an arithmetic number, because the mean of its divisors is an integer number (216435).

2⁷²¹⁴⁴⁵ is an apocalyptic number.

It is an amenable number.

721445 is a deficient number, since it is larger than the sum of its proper divisors (144295).

721445 is a wasteful number, since it uses less digits than its factorization.

721445 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 144294.

The product of its digits is 1120, while the sum is 23.

The square root of 721445 is about 849.3791850522. The cubic root of 721445 is about 89.6880143997.

The spelling of 721445 in words is "seven hundred twenty-one thousand, four hundred forty-five".