21001202221 has 4 divisors (see below), whose sum is σ = 21089073600. Its totient is φ = 20913330844.

The previous prime is 21001202207. The next prime is 21001202267. The reversal of 21001202221 is 12220210012.

It is a happy number.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 21001202221 - 2¹¹ = 21001200173 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21001200221) 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, 43935331 + ... + 43935808.

It is an arithmetic number, because the mean of its divisors is an integer number (5272268400).

Almost surely, 2^21001202221 is an apocalyptic number.

It is an amenable number.

21001202221 is a deficient number, since it is larger than the sum of its proper divisors (87871379).

21001202221 is an equidigital number, since it uses as much as digits as its factorization.

21001202221 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 87871378.

The product of its (nonzero) digits is 32, while the sum is 13.

Adding to 21001202221 its reverse (12220210012), we get a palindrome (33221412233).

The spelling of 21001202221 in words is "twenty-one billion, one million, two hundred two thousand, two hundred twenty-one".