20949 has 4 divisors (see below), whose sum is σ = 27936. Its totient is φ = 13964.

The previous prime is 20947. The next prime is 20959. The reversal of 20949 is 94902.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 20949 - 2¹ = 20947 is a prime.

It is a D-number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20947) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3489 + ... + 3494.

It is an arithmetic number, because the mean of its divisors is an integer number (6984).

2²⁰⁹⁴⁹ is an apocalyptic number.

It is an amenable number.

20949 is a deficient number, since it is larger than the sum of its proper divisors (6987).

20949 is an equidigital number, since it uses as much as digits as its factorization.

20949 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6986.

The product of its (nonzero) digits is 648, while the sum is 24.

The square root of 20949 is about 144.7376937774. The cubic root of 20949 is about 27.5668895113.

Subtracting from 20949 its product of nonzero digits (648), we obtain a triangular number (20301 = T₂₀₁).

It can be divided in two parts, 20 and 949, that added together give a palindrome (969).

The spelling of 20949 in words is "twenty thousand, nine hundred forty-nine".