721791 has 40 divisors (see below), whose sum is σ = 1316480. Its totient is φ = 384912.

The previous prime is 721783. The next prime is 721793. The reversal of 721791 is 197127.

It is not a de Polignac number, because 721791 - 2³ = 721783 is a prime.

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

It is a Duffinian number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 721791.

It is not an unprimeable number, because it can be changed into a prime (721793) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 10740 + ... + 10806.

It is an arithmetic number, because the mean of its divisors is an integer number (32912).

2⁷²¹⁷⁹¹ is an apocalyptic number.

721791 is a deficient number, since it is larger than the sum of its proper divisors (594689).

721791 is a wasteful number, since it uses less digits than its factorization.

721791 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 105 (or 96 counting only the distinct ones).

The product of its digits is 882, while the sum is 27.

The square root of 721791 is about 849.5828388097. The cubic root of 721791 is about 89.7023500240.

The spelling of 721791 in words is "seven hundred twenty-one thousand, seven hundred ninety-one".