20749 has 2 divisors, whose sum is σ = 20750. Its totient is φ = 20748.

The previous prime is 20747. The next prime is 20753. The reversal of 20749 is 94702.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12100 + 8649 = 110^2 + 93^2 .

It is a cyclic number.

It is not a de Polignac number, because 20749 - 2¹ = 20747 is a prime.

Together with 20747, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20743) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10374 + 10375.

It is an arithmetic number, because the mean of its divisors is an integer number (10375).

2²⁰⁷⁴⁹ is an apocalyptic number.

It is an amenable number.

20749 is a deficient number, since it is larger than the sum of its proper divisors (1).

20749 is an equidigital number, since it uses as much as digits as its factorization.

20749 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 504, while the sum is 22.

The square root of 20749 is about 144.0451318164. The cubic root of 20749 is about 27.4788818585.

It can be divided in two parts, 207 and 49, that added together give a 8-th power (256 = 2⁸).

The spelling of 20749 in words is "twenty thousand, seven hundred forty-nine".