20993 has 4 divisors (see below), whose sum is σ = 24000. Its totient is φ = 17988.

The previous prime is 20983. The next prime is 21001. The reversal of 20993 is 39902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20993 - 2⁶ = 20929 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (20903) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1493 + ... + 1506.

It is an arithmetic number, because the mean of its divisors is an integer number (6000).

It is a Proth number, since it is equal to 41 ⋅ 2⁹ + 1 and 41 < 2⁹.

2²⁰⁹⁹³ is an apocalyptic number.

It is an amenable number.

20993 is a deficient number, since it is larger than the sum of its proper divisors (3007).

20993 is an equidigital number, since it uses as much as digits as its factorization.

20993 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3006.

The product of its (nonzero) digits is 486, while the sum is 23.

The square root of 20993 is about 144.8896131543. The cubic root of 20993 is about 27.5861759518.

The spelling of 20993 in words is "twenty thousand, nine hundred ninety-three".