21218928 has 20 divisors (see below), whose sum is σ = 54815688. Its totient is φ = 7072960.

The previous prime is 21218893. The next prime is 21218929. The reversal of 21218928 is 82981212.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21218929) 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 3 ways as a sum of consecutive naturals, for example, 220983 + ... + 221078.

Almost surely, 2^21218928 is an apocalyptic number.

It is an amenable number.

21218928 is an abundant number, since it is smaller than the sum of its proper divisors (33596760).

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

21218928 is a wasteful number, since it uses less digits than its factorization.

21218928 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 442072 (or 442066 counting only the distinct ones).

The product of its digits is 4608, while the sum is 33.

The square root of 21218928 is about 4606.4007641542. The cubic root of 21218928 is about 276.8478444255.

The spelling of 21218928 in words is "twenty-one million, two hundred eighteen thousand, nine hundred twenty-eight".