21243421605 has 16 divisors (see below), whose sum is σ = 38845113984. Its totient is φ = 9711278400.

The previous prime is 21243421601. The next prime is 21243421613. The reversal of 21243421605 is 50612434212.

It is not a de Polignac number, because 21243421605 - 2² = 21243421601 is a prime.

It is a super-2 number, since 2×21243421605² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21243421601) 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, 101159046 + ... + 101159255.

It is an arithmetic number, because the mean of its divisors is an integer number (2427819624).

Almost surely, 2^21243421605 is an apocalyptic number.

It is an amenable number.

21243421605 is a deficient number, since it is larger than the sum of its proper divisors (17601692379).

21243421605 is a wasteful number, since it uses less digits than its factorization.

21243421605 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 202318316.

The product of its (nonzero) digits is 11520, while the sum is 30.

Adding to 21243421605 its reverse (50612434212), we get a palindrome (71855855817).

The spelling of 21243421605 in words is "twenty-one billion, two hundred forty-three million, four hundred twenty-one thousand, six hundred five".