21213320021 has 2 divisors, whose sum is σ = 21213320022. Its totient is φ = 21213320020.

The previous prime is 21213320017. The next prime is 21213320077. The reversal of 21213320021 is 12002331212.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 14891320900 + 6321999121 = 122030^2 + 79511^2 .

It is a cyclic number.

It is not a de Polignac number, because 21213320021 - 2² = 21213320017 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21213320221) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10606660010 + 10606660011.

It is an arithmetic number, because the mean of its divisors is an integer number (10606660011).

Almost surely, 2^21213320021 is an apocalyptic number.

It is an amenable number.

21213320021 is a deficient number, since it is larger than the sum of its proper divisors (1).

21213320021 is an equidigital number, since it uses as much as digits as its factorization.

21213320021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 144, while the sum is 17.

Adding to 21213320021 its reverse (12002331212), we get a palindrome (33215651233).

The spelling of 21213320021 in words is "twenty-one billion, two hundred thirteen million, three hundred twenty thousand, twenty-one".