21258123 has 4 divisors (see below), whose sum is σ = 28344168. Its totient is φ = 14172080.

The previous prime is 21258121. The next prime is 21258151. The reversal of 21258123 is 32185212.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21258123 - 2¹ = 21258121 is a prime.

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

It is a junction number, because it is equal to n+sod(n) for n = 21258093 and 21258102.

It is not an unprimeable number, because it can be changed into a prime (21258121) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 3543018 + ... + 3543023.

It is an arithmetic number, because the mean of its divisors is an integer number (7086042).

Almost surely, 2^21258123 is an apocalyptic number.

21258123 is a deficient number, since it is larger than the sum of its proper divisors (7086045).

21258123 is an equidigital number, since it uses as much as digits as its factorization.

21258123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7086044.

The product of its digits is 960, while the sum is 24.

The square root of 21258123 is about 4610.6532075184. The cubic root of 21258123 is about 277.0182013958.

The spelling of 21258123 in words is "twenty-one million, two hundred fifty-eight thousand, one hundred twenty-three".