21518211 has 16 divisors (see below), whose sum is σ = 33707520. Its totient is φ = 12037920.

The previous prime is 21518197. The next prime is 21518219. The reversal of 21518211 is 11281512.

It is not a de Polignac number, because 21518211 - 2⁷ = 21518083 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21518219) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 24651 + ... + 25508.

It is an arithmetic number, because the mean of its divisors is an integer number (2106720).

Almost surely, 2^21518211 is an apocalyptic number.

21518211 is a deficient number, since it is larger than the sum of its proper divisors (12189309).

21518211 is a wasteful number, since it uses less digits than its factorization.

21518211 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 50186.

The product of its digits is 160, while the sum is 21.

The square root of 21518211 is about 4638.7725747228. The cubic root of 21518211 is about 278.1433753125.

Adding to 21518211 its reverse (11281512), we get a palindrome (32799723).

The spelling of 21518211 in words is "twenty-one million, five hundred eighteen thousand, two hundred eleven".