21202121100021 has 4 divisors (see below), whose sum is σ = 28269494800032. Its totient is φ = 14134747400012.

The previous prime is 21202121100007. The next prime is 21202121100049. The reversal of 21202121100021 is 12000112120212.

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 21202121100021 - 2¹⁹ = 21202120575733 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21202121100221) 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, 3533686850001 + ... + 3533686850006.

It is an arithmetic number, because the mean of its divisors is an integer number (7067373700008).

Almost surely, 2^{21202121100021} is an apocalyptic number.

It is an amenable number.

21202121100021 is a deficient number, since it is larger than the sum of its proper divisors (7067373700011).

21202121100021 is an equidigital number, since it uses as much as digits as its factorization.

21202121100021 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 7067373700010.

The product of its (nonzero) digits is 32, while the sum is 15.

Adding to 21202121100021 its reverse (12000112120212), we get a palindrome (33202233220233).

The spelling of 21202121100021 in words is "twenty-one trillion, two hundred two billion, one hundred twenty-one million, one hundred thousand, twenty-one".