21664554 has 8 divisors (see below), whose sum is σ = 43329120. Its totient is φ = 7221516.

The previous prime is 21664529. The next prime is 21664607. The reversal of 21664554 is 45546612.

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

21664554 is an admirable number.

It is a plaindrome in base 11.

It is an unprimeable number.

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 3 ways as a sum of consecutive naturals, for example, 1805374 + ... + 1805385.

It is an arithmetic number, because the mean of its divisors is an integer number (5416140).

Almost surely, 2^21664554 is an apocalyptic number.

21664554 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.

21664554 is a wasteful number, since it uses less digits than its factorization.

21664554 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3610764.

The product of its digits is 28800, while the sum is 33.

The square root of 21664554 is about 4654.5197389204. The cubic root of 21664554 is about 278.7724921691.

The spelling of 21664554 in words is "twenty-one million, six hundred sixty-four thousand, five hundred fifty-four".