20101231981 has 2 divisors, whose sum is σ = 20101231982. Its totient is φ = 20101231980.

The previous prime is 20101231979. The next prime is 20101232023. The reversal of 20101231981 is 18913210102.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 12738733956 + 7362498025 = 112866^2 + 85805^2 .

It is a cyclic number.

It is not a de Polignac number, because 20101231981 - 2¹ = 20101231979 is a prime.

It is a super-2 number, since 2×20101231981² (a number of 21 digits) contains 22 as substring.

Together with 20101231979, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (20101231921) 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, 10050615990 + 10050615991.

It is an arithmetic number, because the mean of its divisors is an integer number (10050615991).

Almost surely, 2^20101231981 is an apocalyptic number.

It is an amenable number.

20101231981 is a deficient number, since it is larger than the sum of its proper divisors (1).

20101231981 is an equidigital number, since it uses as much as digits as its factorization.

20101231981 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 864, while the sum is 28.

The spelling of 20101231981 in words is "twenty billion, one hundred one million, two hundred thirty-one thousand, nine hundred eighty-one".