21508128 has 144 divisors (see below), whose sum is σ = 67931136. Its totient is φ = 6420480.

The previous prime is 21508121. The next prime is 21508153. The reversal of 21508128 is 82180512.

It is a tau number, because it is divible by the number of its divisors (144).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21508121) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 112513 + ... + 112703.

It is an arithmetic number, because the mean of its divisors is an integer number (471744).

Almost surely, 2^21508128 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 21508128, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (33965568).

21508128 is an abundant number, since it is smaller than the sum of its proper divisors (46423008).

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

21508128 is a wasteful number, since it uses less digits than its factorization.

21508128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 247 (or 236 counting only the distinct ones).

The product of its (nonzero) digits is 1280, while the sum is 27.

The square root of 21508128 is about 4637.6856297080. The cubic root of 21508128 is about 278.0999243984.

The spelling of 21508128 in words is "twenty-one million, five hundred eight thousand, one hundred twenty-eight".