21216873 has 8 divisors (see below), whose sum is σ = 29053888. Its totient is φ = 13762224.

The previous prime is 21216869. The next prime is 21216883. The reversal of 21216873 is 37861212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21216873 - 2² = 21216869 is a prime.

It is a Duffinian number.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 21216873.

It is not an unprimeable number, because it can be changed into a prime (21216883) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 95461 + ... + 95682.

It is an arithmetic number, because the mean of its divisors is an integer number (3631736).

Almost surely, 2^21216873 is an apocalyptic number.

It is an amenable number.

21216873 is a deficient number, since it is larger than the sum of its proper divisors (7837015).

21216873 is a wasteful number, since it uses less digits than its factorization.

21216873 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 191183.

The product of its digits is 4032, while the sum is 30.

The square root of 21216873 is about 4606.1776995683. The cubic root of 21216873 is about 276.8389067970.

Subtracting from 21216873 its product of digits (4032), we obtain a triangular number (21212841 = T₆₅₁₃).

The spelling of 21216873 in words is "twenty-one million, two hundred sixteen thousand, eight hundred seventy-three".