133865981 has 2 divisors, whose sum is σ = 133865982. Its totient is φ = 133865980.

The previous prime is 133865947. The next prime is 133865983. The reversal of 133865981 is 189568331.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 126922756 + 6943225 = 11266^2 + 2635^2 .

It is a cyclic number.

It is not a de Polignac number, because 133865981 - 2¹⁸ = 133603837 is a prime.

It is a super-2 number, since 2×133865981² = 35840201738184722, which contains 22 as substring.

Together with 133865983, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (133865983) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 66932990 + 66932991.

It is an arithmetic number, because the mean of its divisors is an integer number (66932991).

Almost surely, 2^133865981 is an apocalyptic number.

It is an amenable number.

133865981 is a deficient number, since it is larger than the sum of its proper divisors (1).

133865981 is an equidigital number, since it uses as much as digits as its factorization.

133865981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 155520, while the sum is 44.

The square root of 133865981 is about 11570.0467155496. The cubic root of 133865981 is about 511.5523392679.

The spelling of 133865981 in words is "one hundred thirty-three million, eight hundred sixty-five thousand, nine hundred eighty-one".