21021121081 has 2 divisors, whose sum is σ = 21021121082. Its totient is φ = 21021121080.

The previous prime is 21021121007. The next prime is 21021121103. The reversal of 21021121081 is 18012112012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 13712410000 + 7308711081 = 117100^2 + 85491^2 .

It is a cyclic number.

It is not a de Polignac number, because 21021121081 - 2¹¹ = 21021119033 is a prime.

It is a super-2 number, since 2×21021121081² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21421121081) 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 as a sum of consecutive naturals, namely, 10510560540 + 10510560541.

It is an arithmetic number, because the mean of its divisors is an integer number (10510560541).

Almost surely, 2^21021121081 is an apocalyptic number.

It is an amenable number.

21021121081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21021121081 is an equidigital number, since it uses as much as digits as its factorization.

21021121081 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 19.

Adding to 21021121081 its reverse (18012112012), we get a palindrome (39033233093).

The spelling of 21021121081 in words is "twenty-one billion, twenty-one million, one hundred twenty-one thousand, eighty-one".