21213123 has 8 divisors (see below), whose sum is σ = 29259600. Its totient is φ = 13654368.

The previous prime is 21213119. The next prime is 21213149. The reversal of 21213123 is 32131212.

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

It is not a de Polignac number, because 21213123 - 2² = 21213119 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21213163) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 121828 + ... + 122001.

It is an arithmetic number, because the mean of its divisors is an integer number (3657450).

Almost surely, 2^21213123 is an apocalyptic number.

21213123 is a deficient number, since it is larger than the sum of its proper divisors (8046477).

21213123 is a wasteful number, since it uses less digits than its factorization.

21213123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 243861.

The product of its digits is 72, while the sum is 15.

The square root of 21213123 is about 4605.7706195598. The cubic root of 21213123 is about 276.8225957684.

Adding to 21213123 its reverse (32131212), we get a palindrome (53344335).

The spelling of 21213123 in words is "twenty-one million, two hundred thirteen thousand, one hundred twenty-three".