20647 has 4 divisors (see below), whose sum is σ = 22536.
Its totient is φ = 18760.
The previous prime is 20641. The next prime is 20663. The reversal of 20647 is 74602.
Multipling 20647 by its sum of digits (19), we get a palindrome (392293).
It can be divided in two parts, 206 and 47, that added together give a triangular number (253 = T22).
It is a semiprime because it is the product of two primes.
It is a cyclic number.
It is not a de Polignac number, because 20647 - 23 = 20639 is a prime.
It is a Duffinian number.
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 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, 928 + ... + 949.
It is an arithmetic number, because the mean of its divisors is an integer number (5634).
220647 is an apocalyptic number.
20647 is a deficient number, since it is larger than the sum of its proper divisors (1889).
20647 is a wasteful number, since it uses less digits than its factorization.
20647 is an odious number, because the sum of its binary digits is odd.
The sum of its prime factors is 1888.
The product of its (nonzero) digits is 336, while the sum is 19.
The square root of 20647 is about 143.6906399178.
The cubic root of 20647 is about 27.4337800645.
The spelling of 20647 in words is "twenty thousand, six hundred forty-seven".