21011012221 has 4 divisors (see below), whose sum is σ = 21247091100. Its totient is φ = 20774933344.

The previous prime is 21011012177. The next prime is 21011012273. The reversal of 21011012221 is 12221011012.

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 8086505625 + 12924506596 = 89925^2 + 113686^2 .

It is a cyclic number.

It is not a de Polignac number, because 21011012221 - 2⁹ = 21011011709 is a prime.

It is a super-2 number, since 2×21011012221² (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 (21011012291) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 118039306 + ... + 118039483.

It is an arithmetic number, because the mean of its divisors is an integer number (5311772775).

Almost surely, 2^21011012221 is an apocalyptic number.

It is an amenable number.

21011012221 is a deficient number, since it is larger than the sum of its proper divisors (236078879).

21011012221 is an equidigital number, since it uses as much as digits as its factorization.

21011012221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 236078878.

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

Adding to 21011012221 its reverse (12221011012), we get a palindrome (33232023233).

The spelling of 21011012221 in words is "twenty-one billion, eleven million, twelve thousand, two hundred twenty-one".