20865641 has 2 divisors, whose sum is σ = 20865642. Its totient is φ = 20865640.

The previous prime is 20865617. The next prime is 20865643. The reversal of 20865641 is 14656802.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19175641 + 1690000 = 4379^2 + 1300^2 .

It is a cyclic number.

It is not a de Polignac number, because 20865641 - 2¹⁰ = 20864617 is a prime.

Together with 20865643, it forms a pair of twin primes.

It is a Chen prime.

It is a junction number, because it is equal to n+sod(n) for n = 20865598 and 20865607.

It is not a weakly prime, because it can be changed into another prime (20865643) 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, 10432820 + 10432821.

It is an arithmetic number, because the mean of its divisors is an integer number (10432821).

Almost surely, 2^20865641 is an apocalyptic number.

It is an amenable number.

20865641 is a deficient number, since it is larger than the sum of its proper divisors (1).

20865641 is an equidigital number, since it uses as much as digits as its factorization.

20865641 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 11520, while the sum is 32.

The square root of 20865641 is about 4567.8924024105. The cubic root of 20865641 is about 275.3027673656.

The spelling of 20865641 in words is "twenty million, eight hundred sixty-five thousand, six hundred forty-one".