21875215 has 4 divisors (see below), whose sum is σ = 26250264. Its totient is φ = 17500168.

The previous prime is 21875207. The next prime is 21875233. The reversal of 21875215 is 51257812.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21875215 - 2³ = 21875207 is a prime.

It is a Smith number, since the sum of its digits (31) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2187517 + ... + 2187526.

It is an arithmetic number, because the mean of its divisors is an integer number (6562566).

Almost surely, 2^21875215 is an apocalyptic number.

21875215 is a deficient number, since it is larger than the sum of its proper divisors (4375049).

21875215 is an equidigital number, since it uses as much as digits as its factorization.

21875215 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4375048.

The product of its digits is 5600, while the sum is 31.

The square root of 21875215 is about 4677.0947178778. The cubic root of 21875215 is about 279.6731517769.

The spelling of 21875215 in words is "twenty-one million, eight hundred seventy-five thousand, two hundred fifteen".