20805613 has 2 divisors, whose sum is σ = 20805614. Its totient is φ = 20805612.

The previous prime is 20805611. The next prime is 20805623. The reversal of 20805613 is 31650802.

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., 16793604 + 4012009 = 4098^2 + 2003^2 .

It is a cyclic number.

It is not a de Polignac number, because 20805613 - 2¹ = 20805611 is a prime.

Together with 20805611, 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 (20805611) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10402806 + 10402807.

It is an arithmetic number, because the mean of its divisors is an integer number (10402807).

Almost surely, 2^20805613 is an apocalyptic number.

It is an amenable number.

20805613 is a deficient number, since it is larger than the sum of its proper divisors (1).

20805613 is an equidigital number, since it uses as much as digits as its factorization.

20805613 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1440, while the sum is 25.

The square root of 20805613 is about 4561.3170247199. The cubic root of 20805613 is about 275.0385092077.

The spelling of 20805613 in words is "twenty million, eight hundred five thousand, six hundred thirteen".