20688656 has 40 divisors (see below), whose sum is σ = 42211584. Its totient is φ = 9809280.

The previous prime is 20688649. The next prime is 20688659. The reversal of 20688656 is 65688602.

It is not an unprimeable number, because it can be changed into a prime (20688659) 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, 25895 + ... + 26681.

Almost surely, 2^20688656 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 20688656, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21105792).

20688656 is an abundant number, since it is smaller than the sum of its proper divisors (21522928).

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

20688656 is a wasteful number, since it uses less digits than its factorization.

20688656 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 879 (or 873 counting only the distinct ones).

The product of its (nonzero) digits is 138240, while the sum is 41.

The square root of 20688656 is about 4548.4784269028. The cubic root of 20688656 is about 274.5221718803.

The spelling of 20688656 in words is "twenty million, six hundred eighty-eight thousand, six hundred fifty-six".