1721728 has 16 divisors (see below), whose sum is σ = 3430260.
Its totient is φ = 860800.
The previous prime is 1721719. The next prime is 1721729. The reversal of 1721728 is 8271271.
Adding to 1721728 its product of digits (1568), we get a triangular number (1723296 = T1856).
Adding to 1721728 its reverse (8271271), we get a palindrome (9992999).
It is a tau number, because it is divible by the number of its divisors (16).
It is a Smith number, since the sum of its digits (28) coincides with the sum of the digits of its prime factors.
It is a junction number, because it is equal to n+sod(n) for n = 1721696 and 1721705.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (1721729) 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 as a sum of consecutive naturals, namely, 6598 + ... + 6853.
21721728 is an apocalyptic number.
It is an amenable number.
1721728 is a deficient number, since it is larger than the sum of its proper divisors (1708532).
1721728 is an equidigital number, since it uses as much as digits as its factorization.
1721728 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 13465 (or 13453 counting only the distinct ones).
The product of its digits is 1568, while the sum is 28.
The square root of 1721728 is about 1312.1463333028.
The cubic root of 1721728 is about 119.8546388036.
The spelling of 1721728 in words is "one million, seven hundred twenty-one thousand, seven hundred twenty-eight".