21121304423 has 4 divisors (see below), whose sum is σ = 21142490280. Its totient is φ = 21100118568.

The previous prime is 21121304417. The next prime is 21121304497. The reversal of 21121304423 is 32440312112.

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

It is a cyclic number.

It is not a de Polignac number, because 21121304423 - 2²⁴ = 21104527207 is a prime.

It is a super-2 number, since 2×21121304423² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121300423) 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, 10591433 + ... + 10593426.

It is an arithmetic number, because the mean of its divisors is an integer number (5285622570).

Almost surely, 2^21121304423 is an apocalyptic number.

21121304423 is a deficient number, since it is larger than the sum of its proper divisors (21185857).

21121304423 is an equidigital number, since it uses as much as digits as its factorization.

21121304423 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21185856.

The product of its (nonzero) digits is 1152, while the sum is 23.

Adding to 21121304423 its reverse (32440312112), we get a palindrome (53561616535).

The spelling of 21121304423 in words is "twenty-one billion, one hundred twenty-one million, three hundred four thousand, four hundred twenty-three".