20666556 has 48 divisors (see below), whose sum is σ = 54475680. Its totient is φ = 6773760.

The previous prime is 20666551. The next prime is 20666557. The reversal of 20666556 is 65566602.

It is a super-2 number, since 2×20666556² = 854213073802272, which contains 22 as substring.

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

It is a self number, because there is not a number n which added to its sum of digits gives 20666556.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20666551) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 5020 + ... + 8156.

It is an arithmetic number, because the mean of its divisors is an integer number (1134910).

Almost surely, 2^20666556 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 20666556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27237840).

20666556 is an abundant number, since it is smaller than the sum of its proper divisors (33809124).

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

20666556 is a wasteful number, since it uses less digits than its factorization.

20666556 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3211 (or 3203 counting only the distinct ones).

The product of its (nonzero) digits is 64800, while the sum is 36.

The square root of 20666556 is about 4546.0483939351. The cubic root of 20666556 is about 274.4243871884.

The spelling of 20666556 in words is "twenty million, six hundred sixty-six thousand, five hundred fifty-six".