21013000081 has 2 divisors, whose sum is σ = 21013000082. Its totient is φ = 21013000080.

The previous prime is 21013000079. The next prime is 21013000109. The reversal of 21013000081 is 18000031012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18387360000 + 2625640081 = 135600^2 + 51241^2 .

It is a cyclic number.

It is not a de Polignac number, because 21013000081 - 2¹ = 21013000079 is a prime.

It is a super-2 number, since 2×21013000081² (a number of 21 digits) contains 22 as substring.

Together with 21013000079, it forms a pair of twin primes.

It is not a weakly prime, because it can be changed into another prime (21013001081) 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, 10506500040 + 10506500041.

It is an arithmetic number, because the mean of its divisors is an integer number (10506500041).

Almost surely, 2^21013000081 is an apocalyptic number.

It is an amenable number.

21013000081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21013000081 is an equidigital number, since it uses as much as digits as its factorization.

21013000081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 48, while the sum is 16.

Adding to 21013000081 its reverse (18000031012), we get a palindrome (39013031093).

The spelling of 21013000081 in words is "twenty-one billion, thirteen million, eighty-one", and thus it is an aban number and an uban number.