20665851 has 8 divisors (see below), whose sum is σ = 27637584. Its totient is φ = 13735680.

The previous prime is 20665849. The next prime is 20665859. The reversal of 20665851 is 15856602.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20665851 - 2¹ = 20665849 is a prime.

It is not an unprimeable number, because it can be changed into a prime (20665859) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 9210 + ... + 11231.

It is an arithmetic number, because the mean of its divisors is an integer number (3454698).

Almost surely, 2^20665851 is an apocalyptic number.

20665851 is a deficient number, since it is larger than the sum of its proper divisors (6971733).

20665851 is a wasteful number, since it uses less digits than its factorization.

20665851 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 20781.

The product of its (nonzero) digits is 14400, while the sum is 33.

The square root of 20665851 is about 4545.9708534041. The cubic root of 20665851 is about 274.4212666654.

Subtracting from 20665851 its reverse (15856602), we obtain a square (4809249 = 2193²).

The spelling of 20665851 in words is "twenty million, six hundred sixty-five thousand, eight hundred fifty-one".