20825 has 18 divisors (see below), whose sum is σ = 31806. Its totient is φ = 13440.

The previous prime is 20809. The next prime is 20849. The reversal of 20825 is 52802.

20825 = T₁ + T₂ + ... + T₄₉.

It is a happy number.

20825 is a nontrivial binomial coefficient, being equal to C(51, 3).

It can be written as a sum of positive squares in 3 ways, for example, as 3136 + 17689 = 56^2 + 133^2 .

It is not a de Polignac number, because 20825 - 2⁴ = 20809 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (17).

It is a Duffinian number.

It is a Curzon number.

It is an unprimeable number.

It is the 49-th tetrahedral number.

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 17 ways as a sum of consecutive naturals, for example, 1217 + ... + 1233.

It is an arithmetic number, because the mean of its divisors is an integer number (1767).

2²⁰⁸²⁵ is an apocalyptic number.

20825 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

It is an amenable number.

20825 is a deficient number, since it is larger than the sum of its proper divisors (10981).

20825 is a wasteful number, since it uses less digits than its factorization.

20825 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41 (or 29 counting only the distinct ones).

The product of its (nonzero) digits is 160, while the sum is 17.

The square root of 20825 is about 144.3086968966. The cubic root of 20825 is about 27.5123911101.

Multiplying 20825 by its sum of digits (17), we get a square (354025 = 595²).

20825 divided by its sum of digits (17) gives a triangular number (1225 = T₄₉).

The spelling of 20825 in words is "twenty thousand, eight hundred twenty-five".