21001012001221 has 16 divisors (see below), whose sum is σ = 24454478275200. Its totient is φ = 17660889200448.

The previous prime is 21001012001201. The next prime is 21001012001237. The reversal of 21001012001221 is 12210021010012.

It is a cyclic number.

It is not a de Polignac number, because 21001012001221 - 2¹³ = 21001011993029 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001012001201) 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, 19825350 + ... + 20857768.

It is an arithmetic number, because the mean of its divisors is an integer number (1528404892200).

Almost surely, 2^{21001012001221} is an apocalyptic number.

It is an amenable number.

21001012001221 is a deficient number, since it is larger than the sum of its proper divisors (3453466273979).

21001012001221 is a wasteful number, since it uses less digits than its factorization.

21001012001221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1087308.

The product of its (nonzero) digits is 16, while the sum is 13.

Adding to 21001012001221 its reverse (12210021010012), we get a palindrome (33211033011233).

The spelling of 21001012001221 in words is "twenty-one trillion, one billion, twelve million, one thousand, two hundred twenty-one".