21023231081 has 2 divisors, whose sum is σ = 21023231082. Its totient is φ = 21023231080.

The previous prime is 21023231063. The next prime is 21023231107. The reversal of 21023231081 is 18013232012.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20537469481 + 485761600 = 143309^2 + 22040^2 .

It is a cyclic number.

It is not a de Polignac number, because 21023231081 - 2¹⁰ = 21023230057 is a prime.

It is a super-2 number, since 2×21023231081² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21020231081) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10511615540 + 10511615541.

It is an arithmetic number, because the mean of its divisors is an integer number (10511615541).

Almost surely, 2^21023231081 is an apocalyptic number.

It is an amenable number.

21023231081 is a deficient number, since it is larger than the sum of its proper divisors (1).

21023231081 is an equidigital number, since it uses as much as digits as its factorization.

21023231081 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 576, while the sum is 23.

Adding to 21023231081 its reverse (18013232012), we get a palindrome (39036463093).

The spelling of 21023231081 in words is "twenty-one billion, twenty-three million, two hundred thirty-one thousand, eighty-one".