21421434431 has 4 divisors (see below), whose sum is σ = 21421896600. Its totient is φ = 21420972264.

The previous prime is 21421434413. The next prime is 21421434439. The reversal of 21421434431 is 13443412412.

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 21421434431 - 2¹⁸ = 21421172287 is a prime.

It is a super-2 number, since 2×21421434431² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21421434394 and 21421434403.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21421434439) 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, 152696 + ... + 257213.

It is an arithmetic number, because the mean of its divisors is an integer number (5355474150).

Almost surely, 2^21421434431 is an apocalyptic number.

21421434431 is a deficient number, since it is larger than the sum of its proper divisors (462169).

21421434431 is an equidigital number, since it uses as much as digits as its factorization.

21421434431 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 462168.

The product of its digits is 9216, while the sum is 29.

Adding to 21421434431 its reverse (13443412412), we get a palindrome (34864846843).

The spelling of 21421434431 in words is "twenty-one billion, four hundred twenty-one million, four hundred thirty-four thousand, four hundred thirty-one".