21318351 has 4 divisors (see below), whose sum is σ = 28424472. Its totient is φ = 14212232.

The previous prime is 21318343. The next prime is 21318377. The reversal of 21318351 is 15381312.

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 21318351 - 2³ = 21318343 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21308351) by changing a digit.

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, 3553056 + ... + 3553061.

It is an arithmetic number, because the mean of its divisors is an integer number (7106118).

Almost surely, 2^21318351 is an apocalyptic number.

21318351 is a deficient number, since it is larger than the sum of its proper divisors (7106121).

21318351 is an equidigital number, since it uses as much as digits as its factorization.

21318351 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7106120.

The product of its digits is 720, while the sum is 24.

The square root of 21318351 is about 4617.1799834964. The cubic root of 21318351 is about 277.2795684744.

Adding to 21318351 its reverse (15381312), we get a palindrome (36699663).

The spelling of 21318351 in words is "twenty-one million, three hundred eighteen thousand, three hundred fifty-one".