21001010221 has 4 divisors (see below), whose sum is σ = 21001866844. Its totient is φ = 21000153600.

The previous prime is 21001010179. The next prime is 21001010237. The reversal of 21001010221 is 12201010012.

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 6322476196 + 14678534025 = 79514^2 + 121155^2 .

It is a cyclic number.

It is not a de Polignac number, because 21001010221 - 2²⁷ = 20866792493 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 21001010198 and 21001010207.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001011221) 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, 390420 + ... + 440941.

It is an arithmetic number, because the mean of its divisors is an integer number (5250466711).

Almost surely, 2^21001010221 is an apocalyptic number.

It is an amenable number.

21001010221 is a deficient number, since it is larger than the sum of its proper divisors (856623).

21001010221 is an equidigital number, since it uses as much as digits as its factorization.

21001010221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 856622.

The product of its (nonzero) digits is 8, while the sum is 10.

Adding to 21001010221 its reverse (12201010012), we get a palindrome (33202020233).

The spelling of 21001010221 in words is "twenty-one billion, one million, ten thousand, two hundred twenty-one".