21281123 has 8 divisors (see below), whose sum is σ = 21850560. Its totient is φ = 20718760.

The previous prime is 21281111. The next prime is 21281137. The reversal of 21281123 is 32118212.

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 21281123 - 2⁴ = 21281107 is a prime.

It is a super-2 number, since 2×21281123² = 905772392282258, which contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21281095 and 21281104.

It is not an unprimeable number, because it can be changed into a prime (21281153) 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, 4628 + ... + 7998.

It is an arithmetic number, because the mean of its divisors is an integer number (2731320).

Almost surely, 2^21281123 is an apocalyptic number.

21281123 is a deficient number, since it is larger than the sum of its proper divisors (569437).

21281123 is a wasteful number, since it uses less digits than its factorization.

21281123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3537.

The product of its digits is 192, while the sum is 20.

The square root of 21281123 is about 4613.1467568245. The cubic root of 21281123 is about 277.1180710187.

Adding to 21281123 its reverse (32118212), we get a palindrome (53399335).

The spelling of 21281123 in words is "twenty-one million, two hundred eighty-one thousand, one hundred twenty-three".