21208123 has 8 divisors (see below), whose sum is σ = 23045120. Its totient is φ = 19443240.

The previous prime is 21208097. The next prime is 21208127. The reversal of 21208123 is 32180212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21208123 - 2⁵ = 21208091 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (19).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21208123.

It is not an unprimeable number, because it can be changed into a prime (21208127) 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 7 ways as a sum of consecutive naturals, for example, 17415 + ... + 18592.

It is an arithmetic number, because the mean of its divisors is an integer number (2880640).

Almost surely, 2^21208123 is an apocalyptic number.

21208123 is a deficient number, since it is larger than the sum of its proper divisors (1836997).

21208123 is a wasteful number, since it uses less digits than its factorization.

21208123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 36057.

The product of its (nonzero) digits is 192, while the sum is 19.

The square root of 21208123 is about 4605.2277902401. The cubic root of 21208123 is about 276.8008447397.

Adding to 21208123 its reverse (32180212), we get a palindrome (53388335).

The spelling of 21208123 in words is "twenty-one million, two hundred eight thousand, one hundred twenty-three".