20809556 has 24 divisors (see below), whose sum is σ = 37787904. Its totient is φ = 10016640.

The previous prime is 20809553. The next prime is 20809561. The reversal of 20809556 is 65590802.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20809553) 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 7 ways as a sum of consecutive naturals, for example, 34796 + ... + 35388.

It is an arithmetic number, because the mean of its divisors is an integer number (1574496).

Almost surely, 2^20809556 is an apocalyptic number.

It is an amenable number.

20809556 is a deficient number, since it is larger than the sum of its proper divisors (16978348).

20809556 is a wasteful number, since it uses less digits than its factorization.

20809556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 911 (or 909 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 35.

The square root of 20809556 is about 4561.7492259001. The cubic root of 20809556 is about 275.0558828581.

The spelling of 20809556 in words is "twenty million, eight hundred nine thousand, five hundred fifty-six".