1001011981 has 2 divisors, whose sum is σ = 1001011982.
Its totient is φ = 1001011980.
The previous prime is 1001011943. The next prime is 1001011987. The reversal of 1001011981 is 1891101001.
It is a strong prime.
It can be written as a sum of positive squares in only one way, i.e., 874089225 + 126922756 = 29565^2 + 11266^2
It is an emirp because it is prime and its reverse (1891101001) is a distict prime.
It is a cyclic number.
It is not a de Polignac number, because 1001011981 - 27 = 1001011853 is a prime.
It is a super-2 number, since 2×10010119812 = 2004049972211088722, which contains 22 as substring.
It is a congruent number.
It is not a weakly prime, because it can be changed into another prime (1001011987) 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, 500505990 + 500505991.
It is an arithmetic number, because the mean of its divisors is an integer number (500505991).
Almost surely, 21001011981 is an apocalyptic number.
It is an amenable number.
1001011981 is a deficient number, since it is larger than the sum of its proper divisors (1).
1001011981 is an equidigital number, since it uses as much as digits as its factorization.
1001011981 is an odious number, because the sum of its binary digits is odd.
The product of its (nonzero) digits is 72, while the sum is 22.
The square root of 1001011981 is about 31638.7733801423.
The cubic root of 1001011981 is about 1000.3372132744.
Adding to 1001011981 its reverse (1891101001), we get a palindrome (2892112982).
The spelling of 1001011981 in words is "one billion, one million, eleven thousand, nine hundred eighty-one".