21101243221 has 4 divisors (see below), whose sum is σ = 21106689772. Its totient is φ = 21095796672.

The previous prime is 21101243213. The next prime is 21101243263. The reversal of 21101243221 is 12234210112.

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 12407732100 + 8693511121 = 111390^2 + 93239^2 .

It is a cyclic number.

It is not a de Polignac number, because 21101243221 - 2³ = 21101243213 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 (21101243321) 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, 2717460 + ... + 2725213.

It is an arithmetic number, because the mean of its divisors is an integer number (5276672443).

Almost surely, 2^21101243221 is an apocalyptic number.

It is an amenable number.

21101243221 is a deficient number, since it is larger than the sum of its proper divisors (5446551).

21101243221 is an equidigital number, since it uses as much as digits as its factorization.

21101243221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5446550.

The product of its (nonzero) digits is 192, while the sum is 19.

Adding to 21101243221 its reverse (12234210112), we get a palindrome (33335453333).

The spelling of 21101243221 in words is "twenty-one billion, one hundred one million, two hundred forty-three thousand, two hundred twenty-one".