21002432123 has 4 divisors (see below), whose sum is σ = 21101969928. Its totient is φ = 20902894320.

The previous prime is 21002432119. The next prime is 21002432131. The reversal of 21002432123 is 32123420012.

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 21002432123 - 2² = 21002432119 is a prime.

It is a super-4 number, since 4×21002432123⁴ (a number of 42 digits) contains 4444 as substring. Note that it is a super-d number also for d = 2.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21002432095 and 21002432104.

It is not an unprimeable number, because it can be changed into a prime (21002432183) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 49768586 + ... + 49769007.

It is an arithmetic number, because the mean of its divisors is an integer number (5275492482).

Almost surely, 2^21002432123 is an apocalyptic number.

21002432123 is a deficient number, since it is larger than the sum of its proper divisors (99537805).

21002432123 is an equidigital number, since it uses as much as digits as its factorization.

21002432123 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 99537804.

The product of its (nonzero) digits is 576, while the sum is 20.

Adding to 21002432123 its reverse (32123420012), we get a palindrome (53125852135).

The spelling of 21002432123 in words is "twenty-one billion, two million, four hundred thirty-two thousand, one hundred twenty-three".