721618 has 16 divisors (see below), whose sum is σ = 1138176. Its totient is φ = 342720.

The previous prime is 721613. The next prime is 721619. The reversal of 721618 is 816127.

It is an alternating number because its digits alternate between odd and even.

It is a junction number, because it is equal to n+sod(n) for n = 721592 and 721601.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (721613) by changing a digit.

721618 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 7 ways as a sum of consecutive naturals, for example, 6330 + ... + 6442.

It is an arithmetic number, because the mean of its divisors is an integer number (71136).

2⁷²¹⁶¹⁸ is an apocalyptic number.

721618 is a deficient number, since it is larger than the sum of its proper divisors (416558).

721618 is a wasteful number, since it uses less digits than its factorization.

721618 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 249.

The product of its digits is 672, while the sum is 25.

The square root of 721618 is about 849.4810180340. The cubic root of 721618 is about 89.6951827847.

The spelling of 721618 in words is "seven hundred twenty-one thousand, six hundred eighteen".