21312128 has 64 divisors (see below), whose sum is σ = 45239040. Its totient is φ = 9984000.

The previous prime is 21312121. The next prime is 21312149. The reversal of 21312128 is 82121312.

It is a tau number, because it is divible by the number of its divisors (64).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21312121) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 162623 + ... + 162753.

It is an arithmetic number, because the mean of its divisors is an integer number (706860).

Almost surely, 2^21312128 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 21312128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (22619520).

21312128 is an abundant number, since it is smaller than the sum of its proper divisors (23926912).

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

21312128 is a wasteful number, since it uses less digits than its factorization.

21312128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 217 (or 205 counting only the distinct ones).

The product of its digits is 192, while the sum is 20.

The square root of 21312128 is about 4616.5060381202. The cubic root of 21312128 is about 277.2525857952.

The spelling of 21312128 in words is "twenty-one million, three hundred twelve thousand, one hundred twenty-eight".