21001020000221 has 4 divisors (see below), whose sum is σ = 21001036517244. Its totient is φ = 21001003483200.

The previous prime is 21001020000179. The next prime is 21001020000241. The reversal of 21001020000221 is 12200002010012.

It is a happy number.

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 17511170083225 + 3489849916996 = 4184635^2 + 1868114^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21001020000221 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 (21001020000241) 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, 6176300 + ... + 8952581.

It is an arithmetic number, because the mean of its divisors is an integer number (5250259129311).

Almost surely, 2^{21001020000221} is an apocalyptic number.

It is an amenable number.

21001020000221 is a deficient number, since it is larger than the sum of its proper divisors (16517023).

21001020000221 is a wasteful number, since it uses less digits than its factorization.

21001020000221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 16517022.

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21001020000221 its reverse (12200002010012), we get a palindrome (33201022010233).

The spelling of 21001020000221 in words is "twenty-one trillion, one billion, twenty million, two hundred twenty-one", and thus it is an aban number.