1721216 has 64 divisors (see below), whose sum is σ = 4186080. Its totient is φ = 688128.

The previous prime is 1721201. The next prime is 1721227. The reversal of 1721216 is 6121271.

It is a tau number, because it is divible by the number of its divisors (64).

It is an Ulam number.

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 7 ways as a sum of consecutive naturals, for example, 15176 + ... + 15288.

2^1721216 is an apocalyptic number.

1721216 is a gapful number since it is divisible by the number (16) 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 1721216, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (2093040).

1721216 is an abundant number, since it is smaller than the sum of its proper divisors (2464864).

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

1721216 is a wasteful number, since it uses less digits than its factorization.

1721216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 151 (or 139 counting only the distinct ones).

The product of its digits is 168, while the sum is 20.

The square root of 1721216 is about 1311.9512186053. The cubic root of 1721216 is about 119.8427570083.

Adding to 1721216 its reverse (6121271), we get a palindrome (7842487).

The spelling of 1721216 in words is "one million, seven hundred twenty-one thousand, two hundred sixteen".