20605021 has 2 divisors, whose sum is σ = 20605022. Its totient is φ = 20605020.

The previous prime is 20605019. The next prime is 20605043. The reversal of 20605021 is 12050602.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20602521 + 2500 = 4539^2 + 50^2 .

It is a cyclic number.

It is not a de Polignac number, because 20605021 - 2¹ = 20605019 is a prime.

Together with 20605019, it forms a pair of twin primes.

It is a junction number, because it is equal to n+sod(n) for n = 20604986 and 20605004.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20605621) 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, 10302510 + 10302511.

It is an arithmetic number, because the mean of its divisors is an integer number (10302511).

Almost surely, 2^20605021 is an apocalyptic number.

It is an amenable number.

20605021 is a deficient number, since it is larger than the sum of its proper divisors (1).

20605021 is an equidigital number, since it uses as much as digits as its factorization.

20605021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 120, while the sum is 16.

The square root of 20605021 is about 4539.2753827015. The cubic root of 20605021 is about 274.1517487513.

Adding to 20605021 its reverse (12050602), we get a palindrome (32655623).

The spelling of 20605021 in words is "twenty million, six hundred five thousand, twenty-one".