21512205 has 48 divisors (see below), whose sum is σ = 43819776. Its totient is φ = 9624960.

The previous prime is 21512147. The next prime is 21512213. The reversal of 21512205 is 50221512.

It is not a de Polignac number, because 21512205 - 2⁸ = 21511949 is a prime.

It is a congruent number.

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 47 ways as a sum of consecutive naturals, for example, 4764 + ... + 8106.

It is an arithmetic number, because the mean of its divisors is an integer number (912912).

Almost surely, 2^21512205 is an apocalyptic number.

It is an amenable number.

21512205 is an abundant number, since it is smaller than the sum of its proper divisors (22307571).

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

21512205 is a wasteful number, since it uses less digits than its factorization.

21512205 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3378 (or 3375 counting only the distinct ones).

The product of its (nonzero) digits is 200, while the sum is 18.

The square root of 21512205 is about 4638.1251600189. The cubic root of 21512205 is about 278.1174951474.

Adding to 21512205 its reverse (50221512), we get a palindrome (71733717).

It can be divided in two parts, 2151 and 2205, that added together give a square (4356 = 66²).

The spelling of 21512205 in words is "twenty-one million, five hundred twelve thousand, two hundred five".