2181649 has 2 divisors, whose sum is σ = 2181650. Its totient is φ = 2181648.

The previous prime is 2181629. The next prime is 2181659. The reversal of 2181649 is 9461812.

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., 1782225 + 399424 = 1335^2 + 632^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-2181649 is a prime.

2181649 is a lucky number.

It is a zygodrome in base 3.

It is a self number, because there is not a number n which added to its sum of digits gives 2181649.

It is not a weakly prime, because it can be changed into another prime (2181629) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1090824 + 1090825.

It is an arithmetic number, because the mean of its divisors is an integer number (1090825).

2^2181649 is an apocalyptic number.

It is an amenable number.

2181649 is a deficient number, since it is larger than the sum of its proper divisors (1).

2181649 is an equidigital number, since it uses as much as digits as its factorization.

2181649 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 3456, while the sum is 31.

The square root of 2181649 is about 1477.0406223256. The cubic root of 2181649 is about 129.6965109818.

The spelling of 2181649 in words is "two million, one hundred eighty-one thousand, six hundred forty-nine".