21088512 has 126 divisors (see below), whose sum is σ = 63671622. Its totient is φ = 6967296.

The previous prime is 21088469. The next prime is 21088513. The reversal of 21088512 is 21588012.

It can be written as a sum of positive squares in only one way, i.e., 11943936 + 9144576 = 3456^2 + 3024^2 .

It is a Harshad number since it is a multiple of its sum of digits (27).

It is not an unprimeable number, because it can be changed into a prime (21088513) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 13 ways as a sum of consecutive naturals, for example, 186568 + ... + 186680.

Almost surely, 2^21088512 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 21088512, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (31835811).

21088512 is an abundant number, since it is smaller than the sum of its proper divisors (42583110).

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

21088512 is an frugal number, since it uses more digits than its factorization.

21088512 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 147 (or 118 counting only the distinct ones).

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

The square root of 21088512 is about 4592.2229911014. Note that the first 3 decimals coincide. The cubic root of 21088512 is about 276.2794900372.

Subtracting 21088512 from its reverse (21588012), we obtain a triangular number (499500 = T₉₉₉).

The spelling of 21088512 in words is "twenty-one million, eighty-eight thousand, five hundred twelve".