21210220221989 has 2 divisors, whose sum is σ = 21210220221990. Its totient is φ = 21210220221988.

The previous prime is 21210220221929. The next prime is 21210220222007. The reversal of 21210220221989 is 98912202201212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15122897659489 + 6087322562500 = 3888817^2 + 2467250^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21210220221989 is a prime.

It is a super-2 number, since 2×21210220221989² (a number of 27 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21210220221929) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10605110110994 + 10605110110995.

It is an arithmetic number, because the mean of its divisors is an integer number (10605110110995).

Almost surely, 2^{21210220221989} is an apocalyptic number.

It is an amenable number.

21210220221989 is a deficient number, since it is larger than the sum of its proper divisors (1).

21210220221989 is an equidigital number, since it uses as much as digits as its factorization.

21210220221989 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 41472, while the sum is 41.

The spelling of 21210220221989 in words is "twenty-one trillion, two hundred ten billion, two hundred twenty million, two hundred twenty-one thousand, nine hundred eighty-nine".