2009921 has 2 divisors, whose sum is σ = 2009922. Its totient is φ = 2009920.

The previous prime is 2009911. The next prime is 2009923. The reversal of 2009921 is 1299002.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1311025 + 698896 = 1145^2 + 836^2 .

It is a cyclic number.

It is not a de Polignac number, because 2009921 - 2⁶ = 2009857 is a prime.

It is a Sophie Germain prime.

Together with 2009923, it forms a pair of twin primes.

It is a Chen prime.

It is a Curzon number.

It is equal to p₁₄₉₆₃₀ and since 2009921 and 149630 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (2009923) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 1004960 + 1004961.

It is an arithmetic number, because the mean of its divisors is an integer number (1004961).

2^2009921 is an apocalyptic number.

It is an amenable number.

2009921 is a deficient number, since it is larger than the sum of its proper divisors (1).

2009921 is an equidigital number, since it uses as much as digits as its factorization.

2009921 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 324, while the sum is 23.

The square root of 2009921 is about 1417.7168264502. The cubic root of 2009921 is about 126.2000894110.

The spelling of 2009921 in words is "two million, nine thousand, nine hundred twenty-one".