20985560 has 64 divisors (see below), whose sum is σ = 49680000. Its totient is φ = 7967232.

The previous prime is 20985551. The next prime is 20985583. The reversal of 20985560 is 6558902.

It is a Cunningham number, because it is equal to 4581²-1.

It is a plaindrome in base 13.

It is a self number, because there is not a number n which added to its sum of digits gives 20985560.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 91526 + ... + 91754.

It is an arithmetic number, because the mean of its divisors is an integer number (776250).

Almost surely, 2^20985560 is an apocalyptic number.

20985560 is a gapful number since it is divisible by the number (20) 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 20985560, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (24840000).

20985560 is an abundant number, since it is smaller than the sum of its proper divisors (28694440).

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

20985560 is a wasteful number, since it uses less digits than its factorization.

20985560 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 348 (or 344 counting only the distinct ones).

The product of its (nonzero) digits is 21600, while the sum is 35.

The square root of 20985560 is about 4580.9998908535. Note that the first 3 decimals coincide. The cubic root of 20985560 is about 275.8291668446.

The spelling of 20985560 in words is "twenty million, nine hundred eighty-five thousand, five hundred sixty".