721001 has 4 divisors (see below), whose sum is σ = 728532. Its totient is φ = 713472.

The previous prime is 720997. The next prime is 721003. The reversal of 721001 is 100127.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 100127 = 223 ⋅449.

It can be written as a sum of positive squares in 2 ways, for example, as 160000 + 561001 = 400^2 + 749^2 .

It is a cyclic number.

It is not a de Polignac number, because 721001 - 2² = 720997 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is not an unprimeable number, because it can be changed into a prime (721003) 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, 3620 + ... + 3813.

It is an arithmetic number, because the mean of its divisors is an integer number (182133).

2⁷²¹⁰⁰¹ is an apocalyptic number.

It is an amenable number.

721001 is a deficient number, since it is larger than the sum of its proper divisors (7531).

721001 is an equidigital number, since it uses as much as digits as its factorization.

721001 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7530.

The product of its (nonzero) digits is 14, while the sum is 11.

The square root of 721001 is about 849.1177774608. The cubic root of 721001 is about 89.6696116800.

Adding to 721001 its reverse (100127), we get a palindrome (821128).

The spelling of 721001 in words is "seven hundred twenty-one thousand, one", and thus it is an iban number.