21871085 has 4 divisors (see below), whose sum is σ = 26245308. Its totient is φ = 17496864.

The previous prime is 21871067. The next prime is 21871097. The reversal of 21871085 is 58017812.

It is a happy number.

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

It can be written as a sum of positive squares in 2 ways, for example, as 17123044 + 4748041 = 4138^2 + 2179^2 .

It is a cyclic number.

It is not a de Polignac number, because 21871085 - 2⁸ = 21870829 is a prime.

It is a Duffinian number.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2187104 + ... + 2187113.

It is an arithmetic number, because the mean of its divisors is an integer number (6561327).

Almost surely, 2^21871085 is an apocalyptic number.

It is an amenable number.

21871085 is a deficient number, since it is larger than the sum of its proper divisors (4374223).

21871085 is an equidigital number, since it uses as much as digits as its factorization.

21871085 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4374222.

The product of its (nonzero) digits is 4480, while the sum is 32.

The square root of 21871085 is about 4676.6531836346. The cubic root of 21871085 is about 279.6555500784.

Adding to 21871085 its reverse (58017812), we get a palindrome (79888897).

The spelling of 21871085 in words is "twenty-one million, eight hundred seventy-one thousand, eighty-five".