20990556 has 48 divisors (see below), whose sum is σ = 54700800. Its totient is φ = 6960816.

The previous prime is 20990551. The next prime is 20990587. The reversal of 20990556 is 65509902.

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 20990556.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20990551) 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, 28035 + ... + 28773.

It is an arithmetic number, because the mean of its divisors is an integer number (1139600).

Almost surely, 2^20990556 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 20990556, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (27350400).

20990556 is an abundant number, since it is smaller than the sum of its proper divisors (33710244).

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

20990556 is a wasteful number, since it uses less digits than its factorization.

20990556 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1015 (or 1007 counting only the distinct ones).

The product of its (nonzero) digits is 24300, while the sum is 36.

The square root of 20990556 is about 4581.5451542029. The cubic root of 20990556 is about 275.8510538497.

The spelling of 20990556 in words is "twenty million, nine hundred ninety thousand, five hundred fifty-six".