21123105 has 16 divisors (see below), whose sum is σ = 34584000. Its totient is φ = 11003328.

The previous prime is 21123103. The next prime is 21123119. The reversal of 21123105 is 50132112.

It is not a de Polignac number, because 21123105 - 2¹ = 21123103 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (15).

It is not an unprimeable number, because it can be changed into a prime (21123103) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (7) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15730 + ... + 17019.

It is an arithmetic number, because the mean of its divisors is an integer number (2161500).

Almost surely, 2^21123105 is an apocalyptic number.

It is an amenable number.

21123105 is a deficient number, since it is larger than the sum of its proper divisors (13460895).

21123105 is a wasteful number, since it uses less digits than its factorization.

21123105 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32800.

The product of its (nonzero) digits is 60, while the sum is 15.

The square root of 21123105 is about 4595.9879242661. The cubic root of 21123105 is about 276.4304745368.

Adding to 21123105 its reverse (50132112), we get a palindrome (71255217).

The spelling of 21123105 in words is "twenty-one million, one hundred twenty-three thousand, one hundred five".