721005 has 16 divisors (see below), whose sum is σ = 1171584. Its totient is φ = 378560.

The previous prime is 721003. The next prime is 721013. The reversal of 721005 is 500127.

721005 = 264² + 265² + ... + 273².

It is a happy number.

It is not a de Polignac number, because 721005 - 2¹ = 721003 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721003) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 727 + ... + 1403.

It is an arithmetic number, because the mean of its divisors is an integer number (73224).

2⁷²¹⁰⁰⁵ is an apocalyptic number.

It is an amenable number.

721005 is a deficient number, since it is larger than the sum of its proper divisors (450579).

721005 is a wasteful number, since it uses less digits than its factorization.

721005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 756.

The product of its (nonzero) digits is 70, while the sum is 15.

The square root of 721005 is about 849.1201328434. The cubic root of 721005 is about 89.6697775040.

It can be divided in two parts, 7 and 21005, that added together give a palindrome (21012).

The spelling of 721005 in words is "seven hundred twenty-one thousand, five".