21913215 has 16 divisors (see below), whose sum is σ = 35340288. Its totient is φ = 11594016.

The previous prime is 21913201. The next prime is 21913237. The reversal of 21913215 is 51231912.

It is not a de Polignac number, because 21913215 - 2¹¹ = 21911167 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 (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 3847 + ... + 7656.

It is an arithmetic number, because the mean of its divisors is an integer number (2208768).

Almost surely, 2^21913215 is an apocalyptic number.

21913215 is a deficient number, since it is larger than the sum of its proper divisors (13427073).

21913215 is a wasteful number, since it uses less digits than its factorization.

21913215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11638.

The product of its digits is 540, while the sum is 24.

The square root of 21913215 is about 4681.1553061184. The cubic root of 21913215 is about 279.8350005768.

The spelling of 21913215 in words is "twenty-one million, nine hundred thirteen thousand, two hundred fifteen".