2121661 has 2 divisors, whose sum is σ = 2121662. Its totient is φ = 2121660.

The previous prime is 2121653. The next prime is 2121667. The reversal of 2121661 is 1661212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1705636 + 416025 = 1306^2 + 645^2 .

It is a cyclic number.

It is not a de Polignac number, because 2121661 - 2³ = 2121653 is a prime.

2121661 is a lucky number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (2121667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1060830 + 1060831.

It is an arithmetic number, because the mean of its divisors is an integer number (1060831).

2^2121661 is an apocalyptic number.

It is an amenable number.

2121661 is a deficient number, since it is larger than the sum of its proper divisors (1).

2121661 is an equidigital number, since it uses as much as digits as its factorization.

2121661 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 144, while the sum is 19.

The square root of 2121661 is about 1456.5922559179. The cubic root of 2121661 is about 128.4967069059.

Adding to 2121661 its reverse (1661212), we get a palindrome (3782873).

The spelling of 2121661 in words is "two million, one hundred twenty-one thousand, six hundred sixty-one".