21020100221 has 4 divisors (see below), whose sum is σ = 21063984000. Its totient is φ = 20976216444.

The previous prime is 21020100163. The next prime is 21020100239. The reversal of 21020100221 is 12200102012.

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 a de Polignac number, because none of the positive numbers 2^k-21020100221 is a prime.

It is a super-2 number, since 2×21020100221² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21020130221) 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, 21941171 + ... + 21942128.

It is an arithmetic number, because the mean of its divisors is an integer number (5265996000).

Almost surely, 2^21020100221 is an apocalyptic number.

It is an amenable number.

21020100221 is a deficient number, since it is larger than the sum of its proper divisors (43883779).

21020100221 is an equidigital number, since it uses as much as digits as its factorization.

21020100221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 43883778.

The product of its (nonzero) digits is 16, while the sum is 11.

Adding to 21020100221 its reverse (12200102012), we get a palindrome (33220202233).

The spelling of 21020100221 in words is "twenty-one billion, twenty million, one hundred thousand, two hundred twenty-one".