20465 has 4 divisors (see below), whose sum is σ = 24564. Its totient is φ = 16368.

The previous prime is 20443. The next prime is 20477. The reversal of 20465 is 56402.

20465 is nontrivially palindromic in base 4.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 56402 = 2 ⋅28201.

It can be written as a sum of positive squares in 2 ways, for example, as 7921 + 12544 = 89^2 + 112^2 .

It is a cyclic number.

It is not a de Polignac number, because 20465 - 2¹⁰ = 19441 is a prime.

It is a Duffinian number.

It is a plaindrome in base 7.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2042 + ... + 2051.

It is an arithmetic number, because the mean of its divisors is an integer number (6141).

2²⁰⁴⁶⁵ is an apocalyptic number.

It is an amenable number.

20465 is a deficient number, since it is larger than the sum of its proper divisors (4099).

20465 is an equidigital number, since it uses as much as digits as its factorization.

20465 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4098.

The product of its (nonzero) digits is 240, while the sum is 17.

The square root of 20465 is about 143.0559331171. The cubic root of 20465 is about 27.3529339219.

Adding to 20465 its reverse (56402), we get a palindrome (76867).

Subtracting 20465 from its reverse (56402), we obtain a cube (35937 = 33³).

The spelling of 20465 in words is "twenty thousand, four hundred sixty-five".