20561688 has 96 divisors (see below), whose sum is σ = 66044160. Its totient is φ = 5870880.

The previous prime is 20561683. The next prime is 20561689. The reversal of 20561688 is 88616502.

It is a happy number.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20561683) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 12853 + ... + 14363.

It is an arithmetic number, because the mean of its divisors is an integer number (687960).

Almost surely, 2^20561688 is an apocalyptic number.

20561688 is a gapful number since it is divisible by the number (28) 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 20561688, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33022080).

20561688 is an abundant number, since it is smaller than the sum of its proper divisors (45482472).

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

20561688 is a wasteful number, since it uses less digits than its factorization.

20561688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1539 (or 1523 counting only the distinct ones).

The product of its (nonzero) digits is 23040, while the sum is 36.

The square root of 20561688 is about 4534.4997519021. The cubic root of 20561688 is about 273.9594306532.

The spelling of 20561688 in words is "twenty million, five hundred sixty-one thousand, six hundred eighty-eight".