21121021421 has 4 divisors (see below), whose sum is σ = 21148923132. Its totient is φ = 21093119712.

The previous prime is 21121021403. The next prime is 21121021423. The reversal of 21121021421 is 12412012112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 13113456196 + 8007565225 = 114514^2 + 89485^2 .

It is a cyclic number.

It is not a de Polignac number, because 21121021421 - 2¹⁰ = 21121020397 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21121021421.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21121021423) 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, 13949720 + ... + 13951233.

It is an arithmetic number, because the mean of its divisors is an integer number (5287230783).

Almost surely, 2^21121021421 is an apocalyptic number.

It is an amenable number.

21121021421 is a deficient number, since it is larger than the sum of its proper divisors (27901711).

21121021421 is an equidigital number, since it uses as much as digits as its factorization.

21121021421 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27901710.

The product of its (nonzero) digits is 64, while the sum is 17.

Adding to 21121021421 its reverse (12412012112), we get a palindrome (33533033533).

The spelling of 21121021421 in words is "twenty-one billion, one hundred twenty-one million, twenty-one thousand, four hundred twenty-one".