721730 has 8 divisors (see below), whose sum is σ = 1299132. Its totient is φ = 288688.

The previous prime is 721709. The next prime is 721733. The reversal of 721730 is 37127.

It can be written as a sum of positive squares in 2 ways, for example, as 657721 + 64009 = 811^2 + 253^2 .

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

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (721733) by changing a digit.

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, 36077 + ... + 36096.

2⁷²¹⁷³⁰ is an apocalyptic number.

721730 is a deficient number, since it is larger than the sum of its proper divisors (577402).

721730 is a wasteful number, since it uses less digits than its factorization.

721730 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 72180.

The product of its (nonzero) digits is 294, while the sum is 20.

The square root of 721730 is about 849.5469380794. The cubic root of 721730 is about 89.6998229779.

Adding to 721730 its reverse (37127), we get a palindrome (758857).

The spelling of 721730 in words is "seven hundred twenty-one thousand, seven hundred thirty".