21243021421 has 16 divisors (see below), whose sum is σ = 23416467840. Its totient is φ = 19181352960.

The previous prime is 21243021409. The next prime is 21243021427. The reversal of 21243021421 is 12412034212.

It is a cyclic number.

It is not a de Polignac number, because 21243021421 - 2²⁵ = 21209466989 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21243021392 and 21243021401.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21243021427) 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, 36301 + ... + 209293.

It is an arithmetic number, because the mean of its divisors is an integer number (1463529240).

Almost surely, 2^21243021421 is an apocalyptic number.

It is an amenable number.

21243021421 is a deficient number, since it is larger than the sum of its proper divisors (2173446419).

21243021421 is a wasteful number, since it uses less digits than its factorization.

21243021421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 173316.

The product of its (nonzero) digits is 768, while the sum is 22.

Adding to 21243021421 its reverse (12412034212), we get a palindrome (33655055633).

The spelling of 21243021421 in words is "twenty-one billion, two hundred forty-three million, twenty-one thousand, four hundred twenty-one".