721806 has 16 divisors (see below), whose sum is σ = 1468800. Its totient is φ = 236408.

The previous prime is 721793. The next prime is 721843. The reversal of 721806 is 608127.

It is a Curzon number.

It is a congruent number.

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, 666 + ... + 1373.

It is an arithmetic number, because the mean of its divisors is an integer number (91800).

2⁷²¹⁸⁰⁶ is an apocalyptic number.

721806 is an abundant number, since it is smaller than the sum of its proper divisors (746994).

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

721806 is a wasteful number, since it uses less digits than its factorization.

721806 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2103.

The product of its (nonzero) digits is 672, while the sum is 24.

The square root of 721806 is about 849.5916666258. The cubic root of 721806 is about 89.7029714070.

The spelling of 721806 in words is "seven hundred twenty-one thousand, eight hundred six".