20705 has 8 divisors (see below), whose sum is σ = 25704. Its totient is φ = 16000.

The previous prime is 20693. The next prime is 20707. The reversal of 20705 is 50702.

20705 = T₉ + T₁₀ + ... + T₄₉.

It can be written as a sum of positive squares in 4 ways, for example, as 2209 + 18496 = 47^2 + 136^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 20705 - 2⁶ = 20641 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a plaindrome in base 14.

It is a nialpdrome in base 12.

It is a self number, because there is not a number n which added to its sum of digits gives 20705.

It is not an unprimeable number, because it can be changed into a prime (20707) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 155 + ... + 255.

It is an arithmetic number, because the mean of its divisors is an integer number (3213).

2²⁰⁷⁰⁵ is an apocalyptic number.

It is an amenable number.

20705 is a deficient number, since it is larger than the sum of its proper divisors (4999).

20705 is a wasteful number, since it uses less digits than its factorization.

20705 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 147.

The product of its (nonzero) digits is 70, while the sum is 14.

The square root of 20705 is about 143.8923208514. The cubic root of 20705 is about 27.4594443522.

The spelling of 20705 in words is "twenty thousand, seven hundred five".