21121304421 has 16 divisors (see below), whose sum is σ = 32841680000. Its totient is φ = 12069316224.

The previous prime is 21121304417. The next prime is 21121304497. The reversal of 21121304421 is 12440312112.

It is not a de Polignac number, because 21121304421 - 2² = 21121304417 is a prime.

It is a super-2 number, since 2×21121304421² (a number of 21 digits) contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (21).

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121304411) 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, 10261996 + ... + 10264053.

It is an arithmetic number, because the mean of its divisors is an integer number (2052605000).

Almost surely, 2^21121304421 is an apocalyptic number.

21121304421 is a gapful number since it is divisible by the number (21) formed by its first and last digit.

It is an amenable number.

21121304421 is a deficient number, since it is larger than the sum of its proper divisors (11720375579).

21121304421 is an equidigital number, since it uses as much as digits as its factorization.

21121304421 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20526073 (or 20526059 counting only the distinct ones).

The product of its (nonzero) digits is 384, while the sum is 21.

Adding to 21121304421 its reverse (12440312112), we get a palindrome (33561616533).

The spelling of 21121304421 in words is "twenty-one billion, one hundred twenty-one million, three hundred four thousand, four hundred twenty-one".