21115215 has 64 divisors (see below), whose sum is σ = 41817600. Its totient is φ = 10022400.

The previous prime is 21115189. The next prime is 21115229. The reversal of 21115215 is 51251112.

It is not a de Polignac number, because 21115215 - 2¹⁵ = 21082447 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 (11) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 87495 + ... + 87735.

It is an arithmetic number, because the mean of its divisors is an integer number (653400).

Almost surely, 2^21115215 is an apocalyptic number.

21115215 is a deficient number, since it is larger than the sum of its proper divisors (20702385).

21115215 is a wasteful number, since it uses less digits than its factorization.

21115215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 325 (or 319 counting only the distinct ones).

The product of its digits is 100, while the sum is 18.

The square root of 21115215 is about 4595.1294867501. The cubic root of 21115215 is about 276.3960523869.

Adding to 21115215 its reverse (51251112), we get a palindrome (72366327).

The spelling of 21115215 in words is "twenty-one million, one hundred fifteen thousand, two hundred fifteen".