21220010081 has 2 divisors, whose sum is σ = 21220010082. Its totient is φ = 21220010080.

The previous prime is 21220010069. The next prime is 21220010089. The reversal of 21220010081 is 18001002212.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17524464400 + 3695545681 = 132380^2 + 60791^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21220010081 is a prime.

It is a super-2 number, since 2×21220010081² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21220010089) 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, 10610005040 + 10610005041.

It is an arithmetic number, because the mean of its divisors is an integer number (10610005041).

Almost surely, 2^21220010081 is an apocalyptic number.

It is an amenable number.

21220010081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21220010081 is an equidigital number, since it uses as much as digits as its factorization.

21220010081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 64, while the sum is 17.

Adding to 21220010081 its reverse (18001002212), we get a palindrome (39221012293).

The spelling of 21220010081 in words is "twenty-one billion, two hundred twenty million, ten thousand, eighty-one".