20890 has 8 divisors (see below), whose sum is σ = 37620. Its totient is φ = 8352.

The previous prime is 20887. The next prime is 20897. The reversal of 20890 is 9802.

It can be written as a sum of positive squares in 2 ways, for example, as 20449 + 441 = 143^2 + 21^2 .

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20897) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1035 + ... + 1054.

2²⁰⁸⁹⁰ is an apocalyptic number.

20890 is a deficient number, since it is larger than the sum of its proper divisors (16730).

20890 is a wasteful number, since it uses less digits than its factorization.

20890 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2096.

The product of its (nonzero) digits is 144, while the sum is 19.

The square root of 20890 is about 144.5337330868. The cubic root of 20890 is about 27.5409857169.

The spelling of 20890 in words is "twenty thousand, eight hundred ninety".