127999981 has 2 divisors, whose sum is σ = 127999982. Its totient is φ = 127999980.

The previous prime is 127999967. The next prime is 128000003. The reversal of 127999981 is 189999721.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 105247081 + 22752900 = 10259^2 + 4770^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-127999981 is a prime.

It is a super-2 number, since 2×127999981² = 32767990272000722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (127999901) 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, 63999990 + 63999991.

It is an arithmetic number, because the mean of its divisors is an integer number (63999991).

Almost surely, 2^127999981 is an apocalyptic number.

It is an amenable number.

127999981 is a deficient number, since it is larger than the sum of its proper divisors (1).

127999981 is an equidigital number, since it uses as much as digits as its factorization.

127999981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 734832, while the sum is 55.

The square root of 127999981 is about 11313.7076592954. The cubic root of 127999981 is about 503.9683950220.

The spelling of 127999981 in words is "one hundred twenty-seven million, nine hundred ninety-nine thousand, nine hundred eighty-one".