21355232421 has 16 divisors (see below), whose sum is σ = 28561268736. Its totient is φ = 14193044976.

The previous prime is 21355232413. The next prime is 21355232449. The reversal of 21355232421 is 12423255312.

It is not a de Polignac number, because 21355232421 - 2³ = 21355232413 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21355232491) 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, 4597126 + ... + 4601768.

It is an arithmetic number, because the mean of its divisors is an integer number (1785079296).

Almost surely, 2^21355232421 is an apocalyptic number.

It is an amenable number.

21355232421 is a deficient number, since it is larger than the sum of its proper divisors (7206036315).

21355232421 is a wasteful number, since it uses less digits than its factorization.

21355232421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9032.

The product of its digits is 14400, while the sum is 30.

Adding to 21355232421 its reverse (12423255312), we get a palindrome (33778487733).

The spelling of 21355232421 in words is "twenty-one billion, three hundred fifty-five million, two hundred thirty-two thousand, four hundred twenty-one".