21515212 has 12 divisors (see below), whose sum is σ = 39288816. Its totient is φ = 10289840.

The previous prime is 21515203. The next prime is 21515227. The reversal of 21515212 is 21251512.

It is a self number, because there is not a number n which added to its sum of digits gives 21515212.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 116839 + ... + 117022.

It is an arithmetic number, because the mean of its divisors is an integer number (3274068).

Almost surely, 2^21515212 is an apocalyptic number.

It is an amenable number.

21515212 is a deficient number, since it is larger than the sum of its proper divisors (17773604).

21515212 is a wasteful number, since it uses less digits than its factorization.

21515212 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 233888 (or 233886 counting only the distinct ones).

The product of its digits is 200, while the sum is 19.

The square root of 21515212 is about 4638.4493098448. The cubic root of 21515212 is about 278.1304530682.

Adding to 21515212 its reverse (21251512), we get a palindrome (42766724).

The spelling of 21515212 in words is "twenty-one million, five hundred fifteen thousand, two hundred twelve".