20806656 has 88 divisors (see below), whose sum is σ = 59837904. Its totient is φ = 6389760.

The previous prime is 20806637. The next prime is 20806661. The reversal of 20806656 is 65660802.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 39676 + ... + 40196.

Almost surely, 2^20806656 is an apocalyptic number.

20806656 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20806656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29918952).

20806656 is an abundant number, since it is smaller than the sum of its proper divisors (39031248).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

20806656 is a wasteful number, since it uses less digits than its factorization.

20806656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 557 (or 539 counting only the distinct ones).

The product of its (nonzero) digits is 17280, while the sum is 33.

The square root of 20806656 is about 4561.4313543010. The cubic root of 20806656 is about 275.0431050888.

The spelling of 20806656 in words is "twenty million, eight hundred six thousand, six hundred fifty-six".