721881 has 6 divisors (see below), whose sum is σ = 1042730. Its totient is φ = 481248.

The previous prime is 721859. The next prime is 721883. The reversal of 721881 is 188127.

721881 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 455625 + 266256 = 675^2 + 516^2 .

It is not a de Polignac number, because 721881 - 2⁵ = 721849 is a prime.

It is a super-2 number, since 2×721881² = 1042224356322, which contains 22 as substring.

It is a Duffinian number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 721881.

It is not an unprimeable number, because it can be changed into a prime (721883) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 40096 + ... + 40113.

2⁷²¹⁸⁸¹ is an apocalyptic number.

It is an amenable number.

721881 is a deficient number, since it is larger than the sum of its proper divisors (320849).

721881 is a wasteful number, since it uses less digits than its factorization.

721881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 80215 (or 80212 counting only the distinct ones).

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

The square root of 721881 is about 849.6358043303. The cubic root of 721881 is about 89.7060781928.

It can be divided in two parts, 72 and 1881, that added together give a triangular number (1953 = T₆₂).

The spelling of 721881 in words is "seven hundred twenty-one thousand, eight hundred eighty-one".