21000512 has 56 divisors (see below), whose sum is σ = 46000416. Its totient is φ = 9451008.

The previous prime is 21000509. The next prime is 21000517. The reversal of 21000512 is 21500012.

It is a junction number, because it is equal to n+sod(n) for n = 21000493 and 21000502.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000517) 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 7 ways as a sum of consecutive naturals, for example, 35483 + ... + 36069.

It is an arithmetic number, because the mean of its divisors is an integer number (821436).

Almost surely, 2^21000512 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 21000512, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (23000208).

21000512 is an abundant number, since it is smaller than the sum of its proper divisors (24999904).

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

21000512 is a wasteful number, since it uses less digits than its factorization.

21000512 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 655 (or 645 counting only the distinct ones).

The product of its (nonzero) digits is 20, while the sum is 11.

The square root of 21000512 is about 4582.6315583952. The cubic root of 21000512 is about 275.8946597932.

Adding to 21000512 its reverse (21500012), we get a palindrome (42500524).

Subtracting 21000512 from its reverse (21500012), we obtain a triangular number (499500 = T₉₉₉).

It can be divided in two parts, 21000 and 512, that added together give a palindrome (21512).

The spelling of 21000512 in words is "twenty-one million, five hundred twelve", and thus it is an aban number.