21010220021221 has 8 divisors (see below), whose sum is σ = 21022869688344. Its totient is φ = 20997571449600.

The previous prime is 21010220021179. The next prime is 21010220021237. The reversal of 21010220021221 is 12212002201012.

It is a happy number.

It can be written as a sum of positive squares in 4 ways, for example, as 1648116764100 + 19362103257121 = 1283790^2 + 4400239^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21010220021221 - 2¹⁵ = 21010219988453 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21010220021195 and 21010220021204.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21010220021321) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 39859041 + ... + 40382713.

It is an arithmetic number, because the mean of its divisors is an integer number (2627858711043).

Almost surely, 2^{21010220021221} is an apocalyptic number.

It is an amenable number.

21010220021221 is a deficient number, since it is larger than the sum of its proper divisors (12649667123).

21010220021221 is a wasteful number, since it uses less digits than its factorization.

21010220021221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 547751.

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

Adding to 21010220021221 its reverse (12212002201012), we get a palindrome (33222222222233).

The spelling of 21010220021221 in words is "twenty-one trillion, ten billion, two hundred twenty million, twenty-one thousand, two hundred twenty-one".