21001002001221 has 16 divisors (see below), whose sum is σ = 31002836064768. Its totient is φ = 12537911641200.

The previous prime is 21001002001193. The next prime is 21001002001223. The reversal of 21001002001221 is 12210020010012.

It is not a de Polignac number, because 21001002001221 - 2¹⁰ = 21001002000197 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21001002001197 and 21001002001206.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001002001223) 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, 4749206745 + ... + 4749211166.

It is an arithmetic number, because the mean of its divisors is an integer number (1937677254048).

Almost surely, 2^{21001002001221} is an apocalyptic number.

It is an amenable number.

21001002001221 is a deficient number, since it is larger than the sum of its proper divisors (10001834063547).

21001002001221 is a wasteful number, since it uses less digits than its factorization.

21001002001221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9498417992.

The product of its (nonzero) digits is 16, while the sum is 12.

Adding to 21001002001221 its reverse (12210020010012), we get a palindrome (33211022011233).

The spelling of 21001002001221 in words is "twenty-one trillion, one billion, two million, one thousand, two hundred twenty-one".