20661909 has 16 divisors (see below), whose sum is σ = 28413504. Its totient is φ = 13347200.

The previous prime is 20661881. The next prime is 20661913. The reversal of 20661909 is 90916602.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 20661909 - 2⁹ = 20661397 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 20661909.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20661959) 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 in 15 ways as a sum of consecutive naturals, for example, 20794 + ... + 21764.

It is an arithmetic number, because the mean of its divisors is an integer number (1775844).

Almost surely, 2^20661909 is an apocalyptic number.

It is an amenable number.

20661909 is a deficient number, since it is larger than the sum of its proper divisors (7751595).

20661909 is a wasteful number, since it uses less digits than its factorization.

20661909 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1188.

The product of its (nonzero) digits is 5832, while the sum is 33.

The square root of 20661909 is about 4545.5372619747. The cubic root of 20661909 is about 274.4038169860.

The spelling of 20661909 in words is "twenty million, six hundred sixty-one thousand, nine hundred nine".