21084215 has 16 divisors (see below), whose sum is σ = 26611200. Its totient is φ = 16005792.

The previous prime is 21084187. The next prime is 21084227. The reversal of 21084215 is 51248012.

It is not a de Polignac number, because 21084215 - 2¹⁰ = 21083191 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (23).

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15326 + ... + 16644.

It is an arithmetic number, because the mean of its divisors is an integer number (1663200).

Almost surely, 2^21084215 is an apocalyptic number.

21084215 is a deficient number, since it is larger than the sum of its proper divisors (5526985).

21084215 is a wasteful number, since it uses less digits than its factorization.

21084215 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1486.

The product of its (nonzero) digits is 640, while the sum is 23.

The square root of 21084215 is about 4591.7551110659. The cubic root of 21084215 is about 276.2607238386.

It can be divided in two parts, 2108 and 4215, that multiplied together give a triangular number (8885220 = T₄₂₁₅).

The spelling of 21084215 in words is "twenty-one million, eighty-four thousand, two hundred fifteen".