20988 has 36 divisors (see below), whose sum is σ = 58968. Its totient is φ = 6240.

The previous prime is 20983. The next prime is 21001. The reversal of 20988 is 88902.

It is a tau number, because it is divible by the number of its divisors (36).

It is a super-2 number, since 2×20988² = 880992288, which contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20981) by changing a digit.

20988 is an untouchable number, because it is not equal to the sum of proper divisors of any number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 370 + ... + 422.

It is an arithmetic number, because the mean of its divisors is an integer number (1638).

2²⁰⁹⁸⁸ 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 20988, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (29484).

20988 is an abundant number, since it is smaller than the sum of its proper divisors (37980).

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

20988 is a wasteful number, since it uses less digits than its factorization.

20988 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 74 (or 69 counting only the distinct ones).

The product of its (nonzero) digits is 1152, while the sum is 27.

The square root of 20988 is about 144.8723576118. The cubic root of 20988 is about 27.5839856689.

The spelling of 20988 in words is "twenty thousand, nine hundred eighty-eight".