21001221210121 has 4 divisors (see below), whose sum is σ = 21022585627392. Its totient is φ = 20979856792852.

The previous prime is 21001221210107. The next prime is 21001221210173. The reversal of 21001221210121 is 12101212210012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21001221210121 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21001221210095 and 21001221210104.

It is not an unprimeable number, because it can be changed into a prime (21001221210191) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10682207161 + ... + 10682209126.

It is an arithmetic number, because the mean of its divisors is an integer number (5255646406848).

Almost surely, 2^{21001221210121} is an apocalyptic number.

It is an amenable number.

21001221210121 is a deficient number, since it is larger than the sum of its proper divisors (21364417271).

21001221210121 is an equidigital number, since it uses as much as digits as its factorization.

21001221210121 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21364417270.

The product of its (nonzero) digits is 32, while the sum is 16.

Adding to 21001221210121 its reverse (12101212210012), we get a palindrome (33102433420133).

The spelling of 21001221210121 in words is "twenty-one trillion, one billion, two hundred twenty-one million, two hundred ten thousand, one hundred twenty-one".