1721905 has 8 divisors (see below), whose sum is σ = 2073384. Its totient is φ = 1372800.

The previous prime is 1721903. The next prime is 1721911. The reversal of 1721905 is 5091271.

It can be written as a sum of positive squares in 4 ways, for example, as 223729 + 1498176 = 473^2 + 1224^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1721905 - 2¹ = 1721903 is a prime.

It is an Ulam number.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1721905.

It is not an unprimeable number, because it can be changed into a prime (1721903) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 2275 + ... + 2935.

It is an arithmetic number, because the mean of its divisors is an integer number (259173).

2^1721905 is an apocalyptic number.

It is an amenable number.

1721905 is a deficient number, since it is larger than the sum of its proper divisors (351479).

1721905 is an equidigital number, since it uses as much as digits as its factorization.

1721905 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1187.

The product of its (nonzero) digits is 630, while the sum is 25.

The square root of 1721905 is about 1312.2137783151. The cubic root of 1721905 is about 119.8587458294.

The spelling of 1721905 in words is "one million, seven hundred twenty-one thousand, nine hundred five".