1721287 has 4 divisors (see below), whose sum is σ = 1724080. Its totient is φ = 1718496.

The previous prime is 1721273. The next prime is 1721299. The reversal of 1721287 is 7821271.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 1721287 - 2¹¹ = 1719239 is a prime.

It is a Duffinian number.

1721287 is a lucky number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1721227) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 18 + ... + 1855.

It is an arithmetic number, because the mean of its divisors is an integer number (431020).

2^1721287 is an apocalyptic number.

1721287 is a deficient number, since it is larger than the sum of its proper divisors (2793).

1721287 is an equidigital number, since it uses as much as digits as its factorization.

1721287 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2792.

The product of its digits is 1568, while the sum is 28.

The square root of 1721287 is about 1311.9782772592. The cubic root of 1721287 is about 119.8444048198.

The spelling of 1721287 in words is "one million, seven hundred twenty-one thousand, two hundred eighty-seven".