21351423423 has 16 divisors (see below), whose sum is σ = 31124595456. Its totient is φ = 12911931840.

The previous prime is 21351423397. The next prime is 21351423481. The reversal of 21351423423 is 32432415312.

It is not a de Polignac number, because 21351423423 - 2²⁶ = 21284314559 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21351423493) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 692811 + ... + 722972.

It is an arithmetic number, because the mean of its divisors is an integer number (1945287216).

Almost surely, 2^21351423423 is an apocalyptic number.

21351423423 is a deficient number, since it is larger than the sum of its proper divisors (9773172033).

21351423423 is a wasteful number, since it uses less digits than its factorization.

21351423423 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1416254.

The product of its digits is 17280, while the sum is 30.

Adding to 21351423423 its reverse (32432415312), we get a palindrome (53783838735).

The spelling of 21351423423 in words is "twenty-one billion, three hundred fifty-one million, four hundred twenty-three thousand, four hundred twenty-three".