20641 has 2 divisors, whose sum is σ = 20642. Its totient is φ = 20640.

The previous prime is 20639. The next prime is 20663. The reversal of 20641 is 14602.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14400 + 6241 = 120^2 + 79^2 .

It is a cyclic number.

It is not a de Polignac number, because 20641 - 2¹ = 20639 is a prime.

Together with 20639, it forms a pair of twin primes.

It is a nialpdrome in base 12.

It is not a weakly prime, because it can be changed into another prime (20611) 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 as a sum of consecutive naturals, namely, 10320 + 10321.

It is an arithmetic number, because the mean of its divisors is an integer number (10321).

2²⁰⁶⁴¹ is an apocalyptic number.

It is an amenable number.

20641 is a deficient number, since it is larger than the sum of its proper divisors (1).

20641 is an equidigital number, since it uses as much as digits as its factorization.

20641 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48, while the sum is 13.

The square root of 20641 is about 143.6697602142. The cubic root of 20641 is about 27.4311223963.

The spelling of 20641 in words is "twenty thousand, six hundred forty-one".