21015112081 has 2 divisors, whose sum is σ = 21015112082. Its totient is φ = 21015112080.

The previous prime is 21015112061. The next prime is 21015112087. The reversal of 21015112081 is 18021151012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11142702481 + 9872409600 = 105559^2 + 99360^2 .

It is a cyclic number.

It is not a de Polignac number, because 21015112081 - 2¹⁹ = 21014587793 is a prime.

It is a super-2 number, since 2×21015112081² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21015112087) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10507556040 + 10507556041.

It is an arithmetic number, because the mean of its divisors is an integer number (10507556041).

Almost surely, 2^21015112081 is an apocalyptic number.

It is an amenable number.

21015112081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21015112081 is an equidigital number, since it uses as much as digits as its factorization.

21015112081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 160, while the sum is 22.

Adding to 21015112081 its reverse (18021151012), we get a palindrome (39036263093).

The spelling of 21015112081 in words is "twenty-one billion, fifteen million, one hundred twelve thousand, eighty-one".