1721689 has 2 divisors, whose sum is σ = 1721690. Its totient is φ = 1721688.

The previous prime is 1721683. The next prime is 1721693. The reversal of 1721689 is 9861271.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1488400 + 233289 = 1220^2 + 483^2 .

It is a cyclic number.

It is not a de Polignac number, because 1721689 - 2¹³ = 1713497 is a prime.

It is not a weakly prime, because it can be changed into another prime (1721683) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 860844 + 860845.

It is an arithmetic number, because the mean of its divisors is an integer number (860845).

2^1721689 is an apocalyptic number.

It is an amenable number.

1721689 is a deficient number, since it is larger than the sum of its proper divisors (1).

1721689 is an equidigital number, since it uses as much as digits as its factorization.

1721689 is an evil number, because the sum of its binary digits is even.

The product of its digits is 6048, while the sum is 34.

The square root of 1721689 is about 1312.1314720713. The cubic root of 1721689 is about 119.8537338279.

The spelling of 1721689 in words is "one million, seven hundred twenty-one thousand, six hundred eighty-nine".