20643 has 8 divisors (see below), whose sum is σ = 31488.
Its totient is φ = 11784.
The previous prime is 20641. The next prime is 20663. The reversal of 20643 is 34602.
It is a sphenic number, since it is the product of 3 distinct primes.
It is not a de Polignac number, because 20643 - 21 = 20641 is a prime.
It is a super-2 number, since 2×206432 = 852266898, which contains 22 as substring.
It is an Ulam number.
It is a plaindrome in base 11.
It is a nialpdrome in base 12.
It is a congruent number.
It is not an unprimeable number, because it can be changed into a prime (20641) by changing a digit.
It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 471 + ... + 512.
It is an arithmetic number, because the mean of its divisors is an integer number (3936).
220643 is an apocalyptic number.
20643 is a deficient number, since it is larger than the sum of its proper divisors (10845).
20643 is an equidigital number, since it uses as much as digits as its factorization.
20643 is an evil number, because the sum of its binary digits is even.
The sum of its prime factors is 993.
The product of its (nonzero) digits is 144, while the sum is 15.
The square root of 20643 is about 143.6767204525.
The cubic root of 20643 is about 27.4320083429.
The spelling of 20643 in words is "twenty thousand, six hundred forty-three".