20995 has 16 divisors (see below), whose sum is σ = 30240. Its totient is φ = 13824.

The previous prime is 20983. The next prime is 21001. The reversal of 20995 is 59902.

It is a 9-Lehmer number, since φ(20995) divides (20995-1)⁹.

It is a cyclic number.

It is not a de Polignac number, because 20995 - 2⁵ = 20963 is a prime.

It is a nialpdrome in base 13.

It is an unprimeable number.

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 in 15 ways as a sum of consecutive naturals, for example, 1096 + ... + 1114.

It is an arithmetic number, because the mean of its divisors is an integer number (1890).

2²⁰⁹⁹⁵ is an apocalyptic number.

20995 is a deficient number, since it is larger than the sum of its proper divisors (9245).

20995 is a wasteful number, since it uses less digits than its factorization.

20995 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 54.

The product of its (nonzero) digits is 810, while the sum is 25.

The square root of 20995 is about 144.8965147959. The cubic root of 20995 is about 27.5870519676.

It can be divided in two parts, 20 and 995, that multiplied together give a triangular number (19900 = T₁₉₉).

The spelling of 20995 in words is "twenty thousand, nine hundred ninety-five".