21218371 has 8 divisors (see below), whose sum is σ = 21461184. Its totient is φ = 20977320.

The previous prime is 21218359. The next prime is 21218387. The reversal of 21218371 is 17381212.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21218371 - 2¹³ = 21210179 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21218311) 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, 47676 + ... + 48118.

It is an arithmetic number, because the mean of its divisors is an integer number (2682648).

Almost surely, 2^21218371 is an apocalyptic number.

21218371 is a deficient number, since it is larger than the sum of its proper divisors (242813).

21218371 is a wasteful number, since it uses less digits than its factorization.

21218371 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 881.

The product of its digits is 672, while the sum is 25.

The square root of 21218371 is about 4606.3403044065. The cubic root of 21218371 is about 276.8454219720.

Adding to 21218371 its reverse (17381212), we get a palindrome (38599583).

The spelling of 21218371 in words is "twenty-one million, two hundred eighteen thousand, three hundred seventy-one".