20021100021721 has 2 divisors, whose sum is σ = 20021100021722. Its totient is φ = 20021100021720.

The previous prime is 20021100021667. The next prime is 20021100021737. The reversal of 20021100021721 is 12712000112002.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 18436409287696 + 1584690734025 = 4293764^2 + 1258845^2 .

It is a cyclic number.

It is not a de Polignac number, because 20021100021721 - 2¹³ = 20021100013529 is a prime.

It is not a weakly prime, because it can be changed into another prime (20021101021721) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10010550010860 + 10010550010861.

It is an arithmetic number, because the mean of its divisors is an integer number (10010550010861).

Almost surely, 2^{20021100021721} is an apocalyptic number.

It is an amenable number.

20021100021721 is a deficient number, since it is larger than the sum of its proper divisors (1).

20021100021721 is an equidigital number, since it uses as much as digits as its factorization.

20021100021721 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 112, while the sum is 19.

Adding to 20021100021721 its reverse (12712000112002), we get a palindrome (32733100133723).

The spelling of 20021100021721 in words is "twenty trillion, twenty-one billion, one hundred million, twenty-one thousand, seven hundred twenty-one".