721566 has 12 divisors (see below), whose sum is σ = 1563432. Its totient is φ = 240516.

The previous prime is 721561. The next prime is 721571. The reversal of 721566 is 665127.

It is an interprime number because it is at equal distance from previous prime (721561) and next prime (721571).

It is a Smith number, since the sum of its digits (27) coincides with the sum of the digits of its prime factors.

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 721566.

It is not an unprimeable number, because it can be changed into a prime (721561) by changing a digit.

721566 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 20026 + ... + 20061.

It is an arithmetic number, because the mean of its divisors is an integer number (130286).

2⁷²¹⁵⁶⁶ is an apocalyptic number.

721566 is an abundant number, since it is smaller than the sum of its proper divisors (841866).

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

721566 is a wasteful number, since it uses less digits than its factorization.

721566 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 40095 (or 40092 counting only the distinct ones).

The product of its digits is 2520, while the sum is 27.

The square root of 721566 is about 849.4504105597. The cubic root of 721566 is about 89.6930282460.

The spelling of 721566 in words is "seven hundred twenty-one thousand, five hundred sixty-six".