20558821 has 2 divisors, whose sum is σ = 20558822. Its totient is φ = 20558820.

The previous prime is 20558819. The next prime is 20558827. The reversal of 20558821 is 12885502.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14333796 + 6225025 = 3786^2 + 2495^2 .

It is a cyclic number.

It is not a de Polignac number, because 20558821 - 2¹ = 20558819 is a prime.

Together with 20558819, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20558827) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10279410 + 10279411.

It is an arithmetic number, because the mean of its divisors is an integer number (10279411).

Almost surely, 2^20558821 is an apocalyptic number.

It is an amenable number.

20558821 is a deficient number, since it is larger than the sum of its proper divisors (1).

20558821 is an equidigital number, since it uses as much as digits as its factorization.

20558821 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 6400, while the sum is 31.

The square root of 20558821 is about 4534.1836089863. The cubic root of 20558821 is about 273.9466969678.

The spelling of 20558821 in words is "twenty million, five hundred fifty-eight thousand, eight hundred twenty-one".