21005512 has 32 divisors (see below), whose sum is σ = 44452800. Its totient is φ = 9217600.

The previous prime is 21005503. The next prime is 21005539. The reversal of 21005512 is 21550012.

It is an unprimeable number.

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, 1564 + ... + 6667.

It is an arithmetic number, because the mean of its divisors is an integer number (1389150).

Almost surely, 2^21005512 is an apocalyptic number.

21005512 is a gapful number since it is divisible by the number (22) formed by its first and last digit.

It is an amenable number.

21005512 is an abundant number, since it is smaller than the sum of its proper divisors (23447288).

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

21005512 is a wasteful number, since it uses less digits than its factorization.

21005512 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8277 (or 8273 counting only the distinct ones).

The product of its (nonzero) digits is 100, while the sum is 16.

The square root of 21005512 is about 4583.1770640027. The cubic root of 21005512 is about 275.9165539234.

Adding to 21005512 its reverse (21550012), we get a palindrome (42555524).

The spelling of 21005512 in words is "twenty-one million, five thousand, five hundred twelve".