21888921 has 8 divisors (see below), whose sum is σ = 29408544. Its totient is φ = 14480960.

The previous prime is 21888917. The next prime is 21888943. The reversal of 21888921 is 12988812.

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

It is a cyclic number.

It is not a de Polignac number, because 21888921 - 2² = 21888917 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21888921.

It is not an unprimeable number, because it can be changed into a prime (21888961) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 27456 + ... + 28241.

It is an arithmetic number, because the mean of its divisors is an integer number (3676068).

Almost surely, 2^21888921 is an apocalyptic number.

It is an amenable number.

21888921 is a deficient number, since it is larger than the sum of its proper divisors (7519623).

21888921 is a wasteful number, since it uses less digits than its factorization.

21888921 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55831.

The product of its digits is 18432, while the sum is 39.

The square root of 21888921 is about 4678.5597142710. The cubic root of 21888921 is about 279.7315496780.

The spelling of 21888921 in words is "twenty-one million, eight hundred eighty-eight thousand, nine hundred twenty-one".