21021123 has 4 divisors (see below), whose sum is σ = 28028168. Its totient is φ = 14014080.

The previous prime is 21021107. The next prime is 21021127. The reversal of 21021123 is 32112012.

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

It is not a de Polignac number, because 21021123 - 2⁴ = 21021107 is a prime.

It is a super-2 number, since 2×21021123² = 883775224362258, 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 = 21021099 and 21021108.

It is not an unprimeable number, because it can be changed into a prime (21021127) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3503518 + ... + 3503523.

It is an arithmetic number, because the mean of its divisors is an integer number (7007042).

Almost surely, 2^21021123 is an apocalyptic number.

21021123 is a deficient number, since it is larger than the sum of its proper divisors (7007045).

21021123 is an equidigital number, since it uses as much as digits as its factorization.

21021123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7007044.

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

The square root of 21021123 is about 4584.8798239430. The cubic root of 21021123 is about 275.9848894269.

Adding to 21021123 its reverse (32112012), we get a palindrome (53133135).

The spelling of 21021123 in words is "twenty-one million, twenty-one thousand, one hundred twenty-three".