20666689 has 2 divisors, whose sum is σ = 20666690. Its totient is φ = 20666688.

The previous prime is 20666687. The next prime is 20666743. The reversal of 20666689 is 98666602.

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., 15936064 + 4730625 = 3992^2 + 2175^2 .

It is a cyclic number.

It is not a de Polignac number, because 20666689 - 2¹ = 20666687 is a prime.

It is a super-2 number, since 2×20666689² = 854224068445442, which contains 22 as substring.

Together with 20666687, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (20666687) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10333344 + 10333345.

It is an arithmetic number, because the mean of its divisors is an integer number (10333345).

Almost surely, 2^20666689 is an apocalyptic number.

It is an amenable number.

20666689 is a deficient number, since it is larger than the sum of its proper divisors (1).

20666689 is an equidigital number, since it uses as much as digits as its factorization.

20666689 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 186624, while the sum is 43.

The square root of 20666689 is about 4546.0630220005. The cubic root of 20666689 is about 274.4249758749.

The spelling of 20666689 in words is "twenty million, six hundred sixty-six thousand, six hundred eighty-nine".