21954 has 8 divisors (see below), whose sum is σ = 43920. Its totient is φ = 7316.

The previous prime is 21943. The next prime is 21961. The reversal of 21954 is 45912.

21954 is an esthetic number in base 15, because in such base its adjacent digits differ by 1.

It is a sphenic number, since it is the product of 3 distinct primes.

21954 is an admirable number.

It is a plaindrome in base 15.

It is a self number, because there is not a number n which added to its sum of digits gives 21954.

It is an inconsummate number, since it does not exist a number n which divided by its sum of digits gives 21954.

It is an unprimeable 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 3 ways as a sum of consecutive naturals, for example, 1824 + ... + 1835.

It is an arithmetic number, because the mean of its divisors is an integer number (5490).

2²¹⁹⁵⁴ is an apocalyptic number.

21954 is a primitive abundant number, since it is smaller than the sum of its proper divisors, none of which is abundant.

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

It is a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (21960).

21954 is a wasteful number, since it uses less digits than its factorization.

21954 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3664.

The product of its digits is 360, while the sum is 21.

The square root of 21954 is about 148.1688226315. The cubic root of 21954 is about 28.0008503143. Note that the first 3 decimals are identical.

The spelling of 21954 in words is "twenty-one thousand, nine hundred fifty-four".