21010121221 has 8 divisors (see below), whose sum is σ = 21583548504. Its totient is φ = 20439598080.

The previous prime is 21010121183. The next prime is 21010121227. The reversal of 21010121221 is 12212101012.

It can be written as a sum of positive squares in 4 ways, for example, as 89680900 + 20920440321 = 9470^2 + 144639^2 .

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 21010121221 - 2¹¹ = 21010119173 is a prime.

It is a super-2 number, since 2×21010121221² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21010121227) 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, 711366 + ... + 740311.

It is an arithmetic number, because the mean of its divisors is an integer number (2697943563).

Almost surely, 2^21010121221 is an apocalyptic number.

It is an amenable number.

21010121221 is a deficient number, since it is larger than the sum of its proper divisors (573427283).

21010121221 is a wasteful number, since it uses less digits than its factorization.

21010121221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1452071.

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

Adding to 21010121221 its reverse (12212101012), we get a palindrome (33222222233).

It can be divided in two parts, 2101012 and 1221, that multiplied together give a palindrome (2565335652).

The spelling of 21010121221 in words is "twenty-one billion, ten million, one hundred twenty-one thousand, two hundred twenty-one".