721818 has 16 divisors (see below), whose sum is σ = 1604160. Its totient is φ = 240588.

The previous prime is 721793. The next prime is 721843. The reversal of 721818 is 818127.

It is an interprime number because it is at equal distance from previous prime (721793) and next prime (721843).

It is a Harshad number since it is a multiple of its sum of digits (27).

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

721818 is a modest number, since divided by 1818 gives 72 as remainder.

It is a junction number, because it is equal to n+sod(n) for n = 721791 and 721800.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 721818.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 6630 + ... + 6737.

It is an arithmetic number, because the mean of its divisors is an integer number (100260).

2⁷²¹⁸¹⁸ is an apocalyptic number.

721818 is an abundant number, since it is smaller than the sum of its proper divisors (882342).

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

721818 is a wasteful number, since it uses less digits than its factorization.

721818 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13378 (or 13372 counting only the distinct ones).

The product of its digits is 896, while the sum is 27.

The square root of 721818 is about 849.5987288126. The cubic root of 721818 is about 89.7034685072.

The spelling of 721818 in words is "seven hundred twenty-one thousand, eight hundred eighteen".