21654 has 16 divisors (see below), whose sum is σ = 48240. Its totient is φ = 7200.

The previous prime is 21649. The next prime is 21661. The reversal of 21654 is 45612.

It is a happy number.

It is a Harshad number since it is a multiple of its sum of digits (18).

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

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 7 ways as a sum of consecutive naturals, for example, 147 + ... + 254.

It is an arithmetic number, because the mean of its divisors is an integer number (3015).

2²¹⁶⁵⁴ is an apocalyptic number.

21654 is an abundant number, since it is smaller than the sum of its proper divisors (26586).

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 (24120).

21654 is a wasteful number, since it uses less digits than its factorization.

21654 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 412 (or 406 counting only the distinct ones).

The product of its digits is 240, while the sum is 18.

The square root of 21654 is about 147.1529816212. The cubic root of 21654 is about 27.8727216327.

It can be divided in two parts, 216 and 54, that multiplied together give a square (11664 = 108²).

The spelling of 21654 in words is "twenty-one thousand, six hundred fifty-four".