21020002121221 has 4 divisors (see below), whose sum is σ = 22256472834252. Its totient is φ = 19783531408192.

The previous prime is 21020002121213. The next prime is 21020002121227. The reversal of 21020002121221 is 12212120002012.

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 13926435730596 + 7093566390625 = 3731814^2 + 2663375^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020002121221 - 2³ = 21020002121213 is a prime.

It is a super-2 number, since 2×21020002121221² (a number of 27 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21020002121195 and 21020002121204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020002121227) 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, 618235356490 + ... + 618235356523.

It is an arithmetic number, because the mean of its divisors is an integer number (5564118208563).

Almost surely, 2^{21020002121221} is an apocalyptic number.

It is an amenable number.

21020002121221 is a deficient number, since it is larger than the sum of its proper divisors (1236470713031).

21020002121221 is a wasteful number, since it uses less digits than its factorization.

21020002121221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1236470713030.

The product of its (nonzero) digits is 64, while the sum is 16.

Adding to 21020002121221 its reverse (12212120002012), we get a palindrome (33232122123233).

The spelling of 21020002121221 in words is "twenty-one trillion, twenty billion, two million, one hundred twenty-one thousand, two hundred twenty-one".