20756 has 6 divisors (see below), whose sum is σ = 36330. Its totient is φ = 10376.

The previous prime is 20753. The next prime is 20759. The reversal of 20756 is 65702.

20756 = T₆₈ + T₆₉ + ... + T₇₅.

It is an interprime number because it is at equal distance from previous prime (20753) and next prime (20759).

It can be written as a sum of positive squares in only one way, i.e., 19600 + 1156 = 140^2 + 34^2 .

It is an Ulam number.

It is a congruent number.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 20756.

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 (5) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2591 + ... + 2598.

It is an arithmetic number, because the mean of its divisors is an integer number (6055).

2²⁰⁷⁵⁶ is an apocalyptic number.

It is an amenable number.

20756 is a deficient number, since it is larger than the sum of its proper divisors (15574).

20756 is a wasteful number, since it uses less digits than its factorization.

20756 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5193 (or 5191 counting only the distinct ones).

The product of its (nonzero) digits is 420, while the sum is 20.

The square root of 20756 is about 144.0694277076. The cubic root of 20756 is about 27.4819716547.

Subtracting from 20756 its sum of digits (20), we obtain a 4-th power (20736 = 12⁴).

The spelling of 20756 in words is "twenty thousand, seven hundred fifty-six".