20859661 has 2 divisors, whose sum is σ = 20859662. Its totient is φ = 20859660.

The previous prime is 20859659. The next prime is 20859667. The reversal of 20859661 is 16695802.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17598025 + 3261636 = 4195^2 + 1806^2 .

It is a cyclic number.

It is not a de Polignac number, because 20859661 - 2¹ = 20859659 is a prime.

Together with 20859659, it forms a pair of twin primes.

It is a self number, because there is not a number n which added to its sum of digits gives 20859661.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20859667) 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, 10429830 + 10429831.

It is an arithmetic number, because the mean of its divisors is an integer number (10429831).

Almost surely, 2^20859661 is an apocalyptic number.

It is an amenable number.

20859661 is a deficient number, since it is larger than the sum of its proper divisors (1).

20859661 is an equidigital number, since it uses as much as digits as its factorization.

20859661 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 25920, while the sum is 37.

The square root of 20859661 is about 4567.2377866715. The cubic root of 20859661 is about 275.2764646694.

The spelling of 20859661 in words is "twenty million, eight hundred fifty-nine thousand, six hundred sixty-one".