1331721 has 20 divisors (see below), whose sum is σ = 2042964. Its totient is φ = 864000.

The previous prime is 1331719. The next prime is 1331749. The reversal of 1331721 is 1271331.

It can be written as a sum of positive squares in 2 ways, for example, as 746496 + 585225 = 864^2 + 765^2 .

It is not a de Polignac number, because 1331721 - 2¹ = 1331719 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 1331694 and 1331703.

It is not an unprimeable number, because it can be changed into a prime (1331711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 3121 + ... + 3521.

2^1331721 is an apocalyptic number.

It is an amenable number.

1331721 is a deficient number, since it is larger than the sum of its proper divisors (711243).

1331721 is an equidigital number, since it uses as much as digits as its factorization.

1331721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 454 (or 445 counting only the distinct ones).

The product of its digits is 126, while the sum is 18.

The square root of 1331721 is about 1154.0021663758. The cubic root of 1331721 is about 110.0198586736.

The spelling of 1331721 in words is "one million, three hundred thirty-one thousand, seven hundred twenty-one".