20990 has 8 divisors (see below), whose sum is σ = 37800. Its totient is φ = 8392.

The previous prime is 20983. The next prime is 21001. The reversal of 20990 is 9902.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a Curzon number.

It is a congruent number.

It is an unprimeable number.

20990 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 3 ways as a sum of consecutive naturals, for example, 1040 + ... + 1059.

It is an arithmetic number, because the mean of its divisors is an integer number (4725).

2²⁰⁹⁹⁰ is an apocalyptic number.

20990 is a deficient number, since it is larger than the sum of its proper divisors (16810).

20990 is a wasteful number, since it uses less digits than its factorization.

20990 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2106.

The product of its (nonzero) digits is 162, while the sum is 20.

The square root of 20990 is about 144.8792600754. The cubic root of 20990 is about 27.5848618238.

The spelling of 20990 in words is "twenty thousand, nine hundred ninety".