331721 has 16 divisors (see below), whose sum is σ = 403200. Its totient is φ = 269568.

The previous prime is 331711. The next prime is 331739. The reversal of 331721 is 127133.

It is not a de Polignac number, because 331721 - 2¹⁰ = 330697 is a prime.

It is a super-2 number, since 2×331721² = 220077643682, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (17).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 331721.

It is not an unprimeable number, because it can be changed into a prime (331711) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4160 + ... + 4238.

It is an arithmetic number, because the mean of its divisors is an integer number (25200).

2³³¹⁷²¹ is an apocalyptic number.

It is an amenable number.

331721 is a deficient number, since it is larger than the sum of its proper divisors (71479).

331721 is a wasteful number, since it uses less digits than its factorization.

331721 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 128.

The product of its digits is 126, while the sum is 17.

The square root of 331721 is about 575.9522549656. The cubic root of 331721 is about 69.2241537522.

Adding to 331721 its reverse (127133), we get a palindrome (458854).

The spelling of 331721 in words is "three hundred thirty-one thousand, seven hundred twenty-one".