721736 has 8 divisors (see below), whose sum is σ = 1353270. Its totient is φ = 360864.

The previous prime is 721733. The next prime is 721739. The reversal of 721736 is 637127.

It is an interprime number because it is at equal distance from previous prime (721733) and next prime (721739).

It can be written as a sum of positive squares in only one way, i.e., 481636 + 240100 = 694^2 + 490^2 .

It is a tau number, because it is divible by the number of its divisors (8).

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 721736.

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 as a sum of consecutive naturals, namely, 45101 + ... + 45116.

2⁷²¹⁷³⁶ is an apocalyptic number.

It is an amenable number.

721736 is a deficient number, since it is larger than the sum of its proper divisors (631534).

721736 is a wasteful number, since it uses less digits than its factorization.

721736 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90223 (or 90219 counting only the distinct ones).

The product of its digits is 1764, while the sum is 26.

The square root of 721736 is about 849.5504693660. The cubic root of 721736 is about 89.7000715461.

The spelling of 721736 in words is "seven hundred twenty-one thousand, seven hundred thirty-six".