721506 has 16 divisors (see below), whose sum is σ = 1519200. Its totient is φ = 227808.

The previous prime is 721499. The next prime is 721529. The reversal of 721506 is 605127.

It is an unprimeable number.

721506 is an untouchable number, because it is not equal to the sum of proper divisors of any 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 7 ways as a sum of consecutive naturals, for example, 3051 + ... + 3278.

It is an arithmetic number, because the mean of its divisors is an integer number (94950).

2⁷²¹⁵⁰⁶ is an apocalyptic number.

721506 is an abundant number, since it is smaller than the sum of its proper divisors (797694).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

721506 is a wasteful number, since it uses less digits than its factorization.

721506 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6353.

The product of its (nonzero) digits is 420, while the sum is 21.

The square root of 721506 is about 849.4150928727. The cubic root of 721506 is about 89.6905421113.

The spelling of 721506 in words is "seven hundred twenty-one thousand, five hundred six".