20904421 has 2 divisors, whose sum is σ = 20904422. Its totient is φ = 20904420.

The previous prime is 20904413. The next prime is 20904431. The reversal of 20904421 is 12440902.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19980900 + 923521 = 4470^2 + 961^2 .

It is a cyclic number.

It is not a de Polignac number, because 20904421 - 2³ = 20904413 is a prime.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 20904392 and 20904401.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20904431) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10452210 + 10452211.

It is an arithmetic number, because the mean of its divisors is an integer number (10452211).

Almost surely, 2^20904421 is an apocalyptic number.

It is an amenable number.

20904421 is a deficient number, since it is larger than the sum of its proper divisors (1).

20904421 is an equidigital number, since it uses as much as digits as its factorization.

20904421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 20904421 is about 4572.1352779637. The cubic root of 20904421 is about 275.4732171816.

The spelling of 20904421 in words is "twenty million, nine hundred four thousand, four hundred twenty-one".