21210123 has 32 divisors (see below), whose sum is σ = 32078592. Its totient is φ = 12355200.

The previous prime is 21210109. The next prime is 21210151. The reversal of 21210123 is 32101212.

21210123 is an esthetic number in base 10, because in such base its adjacent digits differ by 1.

It is not a de Polignac number, because 21210123 - 2¹³ = 21201931 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 = 21210099 and 21210108.

It is not an unprimeable number, because it can be changed into a prime (21210103) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 117093 + ... + 117273.

It is an arithmetic number, because the mean of its divisors is an integer number (1002456).

Almost surely, 2^21210123 is an apocalyptic number.

21210123 is a deficient number, since it is larger than the sum of its proper divisors (10868469).

21210123 is a wasteful number, since it uses less digits than its factorization.

21210123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 315.

The product of its (nonzero) digits is 24, while the sum is 12.

The square root of 21210123 is about 4605.4449296458. Note that the first 3 decimals coincide. The cubic root of 21210123 is about 276.8095455614.

Adding to 21210123 its reverse (32101212), we get a palindrome (53311335).

The spelling of 21210123 in words is "twenty-one million, two hundred ten thousand, one hundred twenty-three".