21318621 has 8 divisors (see below), whose sum is σ = 28469760. Its totient is φ = 14189952.

The previous prime is 21318599. The next prime is 21318643. The reversal of 21318621 is 12681312.

It is an interprime number because it is at equal distance from previous prime (21318599) and next prime (21318643).

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

It is not a de Polignac number, because 21318621 - 2⁹ = 21318109 is a prime.

It is a plaindrome in base 13.

It is a junction number, because it is equal to n+sod(n) for n = 21318591 and 21318600.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21318691) 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, 3261 + ... + 7298.

It is an arithmetic number, because the mean of its divisors is an integer number (3558720).

Almost surely, 2^21318621 is an apocalyptic number.

It is an amenable number.

21318621 is a deficient number, since it is larger than the sum of its proper divisors (7151139).

21318621 is a wasteful number, since it uses less digits than its factorization.

21318621 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 11235.

The product of its digits is 576, while the sum is 24.

The square root of 21318621 is about 4617.2092220301. The cubic root of 21318621 is about 277.2807390647.

Adding to 21318621 its reverse (12681312), we get a palindrome (33999933).

The spelling of 21318621 in words is "twenty-one million, three hundred eighteen thousand, six hundred twenty-one".