21871216 has 20 divisors (see below), whose sum is σ = 42854400. Its totient is φ = 10812032.

The previous prime is 21871207. The next prime is 21871237. The reversal of 21871216 is 61217812.

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, 6256 + ... + 9103.

It is an arithmetic number, because the mean of its divisors is an integer number (2142720).

Almost surely, 2^21871216 is an apocalyptic number.

It is an amenable number.

21871216 is a deficient number, since it is larger than the sum of its proper divisors (20983184).

21871216 is a wasteful number, since it uses less digits than its factorization.

21871216 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 15456 (or 15450 counting only the distinct ones).

The product of its digits is 1344, while the sum is 28.

The square root of 21871216 is about 4676.6671893561. The cubic root of 21871216 is about 279.6561084230.

It can be divided in two parts, 2187 and 1216, that added together give a triangular number (3403 = T₈₂).

The spelling of 21871216 in words is "twenty-one million, eight hundred seventy-one thousand, two hundred sixteen".