21612105 has 24 divisors (see below), whose sum is σ = 38755080. Its totient is φ = 11128320.

The previous prime is 21612103. The next prime is 21612119. The reversal of 21612105 is 50121612.

It can be written as a sum of positive squares in 4 ways, for example, as 45369 + 21566736 = 213^2 + 4644^2 .

It is not a de Polignac number, because 21612105 - 2¹ = 21612103 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21612103) 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 23 ways as a sum of consecutive naturals, for example, 6976 + ... + 9585.

It is an arithmetic number, because the mean of its divisors is an integer number (1614795).

Almost surely, 2^21612105 is an apocalyptic number.

It is an amenable number.

21612105 is a deficient number, since it is larger than the sum of its proper divisors (17142975).

21612105 is a wasteful number, since it uses less digits than its factorization.

21612105 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16601 (or 16598 counting only the distinct ones).

The product of its (nonzero) digits is 120, while the sum is 18.

The square root of 21612105 is about 4648.8821236938. The cubic root of 21612105 is about 278.5473447762.

Adding to 21612105 its reverse (50121612), we get a palindrome (71733717).

It can be divided in two parts, 216 and 12105, that added together give a palindrome (12321).

The spelling of 21612105 in words is "twenty-one million, six hundred twelve thousand, one hundred five".