1721664 has 126 divisors (see below), whose sum is σ = 5834634. Its totient is φ = 483840.

The previous prime is 1721659. The next prime is 1721683. The reversal of 1721664 is 4661271.

It can be written as a sum of positive squares in only one way, i.e., 1016064 + 705600 = 1008^2 + 840^2 .

It is a tau number, because it is divible by the number of its divisors (126).

It is a nude number because it is divisible by every one of its digits and also a Zuckerman number because it is divisible by the product of its digits.

It is a congruent number.

It is an unprimeable number.

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 17 ways as a sum of consecutive naturals, for example, 28194 + ... + 28254.

2^1721664 is an apocalyptic number.

1721664 is a gapful number since it is divisible by the number (14) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 1721664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2917317).

1721664 is an abundant number, since it is smaller than the sum of its proper divisors (4112970).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1721664 is a wasteful number, since it uses less digits than its factorization.

1721664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 93 (or 73 counting only the distinct ones).

The product of its digits is 2016, while the sum is 27.

The square root of 1721664 is about 1312.1219455523. The cubic root of 1721664 is about 119.8531537080.

The spelling of 1721664 in words is "one million, seven hundred twenty-one thousand, six hundred sixty-four".