21018105 has 24 divisors (see below), whose sum is σ = 36538632. Its totient is φ = 11176704.

The previous prime is 21018097. The next prime is 21018133. The reversal of 21018105 is 50181012.

It can be written as a sum of positive squares in 4 ways, for example, as 114921 + 20903184 = 339^2 + 4572^2 .

It is not a de Polignac number, because 21018105 - 2³ = 21018097 is a prime.

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

It is an unprimeable number.

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 23 ways as a sum of consecutive naturals, for example, 27387 + ... + 28143.

It is an arithmetic number, because the mean of its divisors is an integer number (1522443).

Almost surely, 2^21018105 is an apocalyptic number.

It is an amenable number.

21018105 is a deficient number, since it is larger than the sum of its proper divisors (15520527).

21018105 is a wasteful number, since it uses less digits than its factorization.

21018105 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1385 (or 1382 counting only the distinct ones).

The product of its (nonzero) digits is 80, while the sum is 18.

The square root of 21018105 is about 4584.5506868176. The cubic root of 21018105 is about 275.9716810894.

Adding to 21018105 its reverse (50181012), we get a palindrome (71199117).

The spelling of 21018105 in words is "twenty-one million, eighteen thousand, one hundred five".