20751 has 4 divisors (see below), whose sum is σ = 27672. Its totient is φ = 13832.

The previous prime is 20749. The next prime is 20753. The reversal of 20751 is 15702.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is an interprime number because it is at equal distance from previous prime (20749) and next prime (20753).

It is a cyclic number.

It is not a de Polignac number, because 20751 - 2¹ = 20749 is a prime.

It is a D-number.

It is a self number, because there is not a number n which added to its sum of digits gives 20751.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20753) 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, 3456 + ... + 3461.

It is an arithmetic number, because the mean of its divisors is an integer number (6918).

2²⁰⁷⁵¹ is an apocalyptic number.

20751 is a deficient number, since it is larger than the sum of its proper divisors (6921).

20751 is an equidigital number, since it uses as much as digits as its factorization.

20751 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6920.

The product of its (nonzero) digits is 70, while the sum is 15.

The square root of 20751 is about 144.0520739177. The cubic root of 20751 is about 27.4797647283.

Subtracting from 20751 its sum of digits (15), we obtain a 4-th power (20736 = 12⁴).

The spelling of 20751 in words is "twenty thousand, seven hundred fifty-one".