21020230981 has 2 divisors, whose sum is σ = 21020230982. Its totient is φ = 21020230980.

The previous prime is 21020230969. The next prime is 21020231027. The reversal of 21020230981 is 18903202012.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19350201025 + 1670029956 = 139105^2 + 40866^2 .

It is a cyclic number.

It is not a de Polignac number, because 21020230981 - 2⁵ = 21020230949 is a prime.

It is a super-2 number, since 2×21020230981² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21020240981) 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, 10510115490 + 10510115491.

It is an arithmetic number, because the mean of its divisors is an integer number (10510115491).

Almost surely, 2^21020230981 is an apocalyptic number.

It is an amenable number.

21020230981 is a deficient number, since it is larger than the sum of its proper divisors (1).

21020230981 is an equidigital number, since it uses as much as digits as its factorization.

21020230981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1728, while the sum is 28.

Adding to 21020230981 its reverse (18903202012), we get a palindrome (39923432993).

The spelling of 21020230981 in words is "twenty-one billion, twenty million, two hundred thirty thousand, nine hundred eighty-one".