21654666 has 24 divisors (see below), whose sum is σ = 51184224. Its totient is φ = 6561960.

The previous prime is 21654649. The next prime is 21654667. The reversal of 21654666 is 66645612.

It is a happy number.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a self number, because there is not a number n which added to its sum of digits gives 21654666.

It is not an unprimeable number, because it can be changed into a prime (21654667) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 54486 + ... + 54881.

It is an arithmetic number, because the mean of its divisors is an integer number (2132676).

Almost surely, 2^21654666 is an apocalyptic number.

21654666 is an abundant number, since it is smaller than the sum of its proper divisors (29529558).

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

21654666 is a wasteful number, since it uses less digits than its factorization.

21654666 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 109386 (or 109383 counting only the distinct ones).

The product of its digits is 51840, while the sum is 36.

The square root of 21654666 is about 4653.4574243244. The cubic root of 21654666 is about 278.7300738503.

It can be divided in two parts, 216546 and 66, that added together give a palindrome (216612).

The spelling of 21654666 in words is "twenty-one million, six hundred fifty-four thousand, six hundred sixty-six".