20812 has 18 divisors (see below), whose sum is σ = 40964. Its totient is φ = 9240.

The previous prime is 20809. The next prime is 20849. The reversal of 20812 is 21802.

It is a junction number, because it is equal to n+sod(n) for n = 20792 and 20801.

It is an unprimeable number.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 463 + ... + 505.

2²⁰⁸¹² is an apocalyptic number.

20812 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

20812 is a deficient number, since it is larger than the sum of its proper divisors (20152).

20812 is a wasteful number, since it uses less digits than its factorization.

20812 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 69 (or 56 counting only the distinct ones).

The product of its (nonzero) digits is 32, while the sum is 13.

The square root of 20812 is about 144.2636475346. The cubic root of 20812 is about 27.5066650512.

Subtracting 20812 from its reverse (21802), we obtain a triangular number (990 = T₄₄).

The spelling of 20812 in words is "twenty thousand, eight hundred twelve".