2181709 has 2 divisors, whose sum is σ = 2181710. Its totient is φ = 2181708.

The previous prime is 2181689. The next prime is 2181719. The reversal of 2181709 is 9071812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 2175625 + 6084 = 1475^2 + 78^2 .

It is a cyclic number.

It is not a de Polignac number, because 2181709 - 2⁷ = 2181581 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2181719) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1090854 + 1090855.

It is an arithmetic number, because the mean of its divisors is an integer number (1090855).

2^2181709 is an apocalyptic number.

It is an amenable number.

2181709 is a deficient number, since it is larger than the sum of its proper divisors (1).

2181709 is an equidigital number, since it uses as much as digits as its factorization.

2181709 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1008, while the sum is 28.

The square root of 2181709 is about 1477.0609330695. The cubic root of 2181709 is about 129.6976999477.

The spelling of 2181709 in words is "two million, one hundred eighty-one thousand, seven hundred nine".