1721005 has 32 divisors (see below), whose sum is σ = 2540160. Its totient is φ = 1102080.

The previous prime is 1721003. The next prime is 1721009. The reversal of 1721005 is 5001271.

It is not a de Polignac number, because 1721005 - 2¹ = 1721003 is a prime.

1721005 is a lucky number.

It is a self number, because there is not a number n which added to its sum of digits gives 1721005.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1721003) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 20694 + ... + 20776.

It is an arithmetic number, because the mean of its divisors is an integer number (79380).

2^1721005 is an apocalyptic number.

1721005 is the 830-th heptagonal number.

It is an amenable number.

1721005 is a deficient number, since it is larger than the sum of its proper divisors (819155).

1721005 is a wasteful number, since it uses less digits than its factorization.

1721005 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 141.

The product of its (nonzero) digits is 70, while the sum is 16.

The square root of 1721005 is about 1311.8708015655. The cubic root of 1721005 is about 119.8378597235.

Adding to 1721005 its reverse (5001271), we get a palindrome (6722276).

The spelling of 1721005 in words is "one million, seven hundred twenty-one thousand, five".