20644 has 12 divisors (see below), whose sum is σ = 39004. Its totient is φ = 9504.

The previous prime is 20641. The next prime is 20663. The reversal of 20644 is 44602.

20644 = 17² + 18² + ... + 40².

It can be written as a sum of positive squares in 2 ways, for example, as 8100 + 12544 = 90^2 + 112^2 .

It is a d-powerful number, because it can be written as 2⁷ + 0 + 6² + 4⁶ + 4⁷ .

It is a plaindrome in base 11.

It is a nialpdrome in base 12 and base 13.

It is a zygodrome 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 pernicious number, because its binary representation contains a prime number (5) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 147 + ... + 250.

It is an amenable number.

20644 is a deficient number, since it is larger than the sum of its proper divisors (18360).

20644 is a wasteful number, since it uses less digits than its factorization.

20644 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 414 (or 412 counting only the distinct ones).

The product of its (nonzero) digits is 192, while the sum is 16.

The square root of 20644 is about 143.6802004453. The cubic root of 20644 is about 27.4324512947.

It can be divided in two parts, 2064 and 4, that multiplied together give a triangular number (8256 = T₁₂₈).

The spelling of 20644 in words is "twenty thousand, six hundred forty-four".