21420231123 has 4 divisors (see below), whose sum is σ = 28560308168. Its totient is φ = 14280154080.

The previous prime is 21420231109. The next prime is 21420231139. The reversal of 21420231123 is 32113202412.

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

It is not a de Polignac number, because 21420231123 - 2²² = 21416036819 is a prime.

It is a super-2 number, since 2×21420231123² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21420231123.

It is not an unprimeable number, because it can be changed into a prime (21420231103) 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, 3570038518 + ... + 3570038523.

It is an arithmetic number, because the mean of its divisors is an integer number (7140077042).

Almost surely, 2^21420231123 is an apocalyptic number.

21420231123 is a deficient number, since it is larger than the sum of its proper divisors (7140077045).

21420231123 is an equidigital number, since it uses as much as digits as its factorization.

21420231123 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7140077044.

The product of its (nonzero) digits is 576, while the sum is 21.

Adding to 21420231123 its reverse (32113202412), we get a palindrome (53533433535).

The spelling of 21420231123 in words is "twenty-one billion, four hundred twenty million, two hundred thirty-one thousand, one hundred twenty-three".