21946 has 4 divisors (see below), whose sum is σ = 32922. Its totient is φ = 10972.

The previous prime is 21943. The next prime is 21961. The reversal of 21946 is 64912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 18225 + 3721 = 135^2 + 61^2 .

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a pancake number, because a pancake can be divided into 21946 parts by 209 straight cuts.

It is not an unprimeable number, because it can be changed into a prime (21943) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5485 + ... + 5488.

2²¹⁹⁴⁶ is an apocalyptic number.

21946 is a deficient number, since it is larger than the sum of its proper divisors (10976).

21946 is a wasteful number, since it uses less digits than its factorization.

21946 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10975.

The product of its digits is 432, while the sum is 22.

The square root of 21946 is about 148.1418239391. The cubic root of 21946 is about 27.9974487471.

The spelling of 21946 in words is "twenty-one thousand, nine hundred forty-six".