138355981 has 2 divisors, whose sum is σ = 138355982. Its totient is φ = 138355980.

The previous prime is 138355963. The next prime is 138356011. The reversal of 138355981 is 189553831.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 72080100 + 66275881 = 8490^2 + 8141^2 .

It is a cyclic number.

It is not a de Polignac number, because 138355981 - 2¹³ = 138347789 is a prime.

It is a super-2 number, since 2×138355981² = 38284754956944722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (138355081) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69177990 + 69177991.

It is an arithmetic number, because the mean of its divisors is an integer number (69177991).

Almost surely, 2^138355981 is an apocalyptic number.

It is an amenable number.

138355981 is a deficient number, since it is larger than the sum of its proper divisors (1).

138355981 is an equidigital number, since it uses as much as digits as its factorization.

138355981 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 129600, while the sum is 43.

The square root of 138355981 is about 11762.4819234718. The cubic root of 138355981 is about 517.2088879008.

The spelling of 138355981 in words is "one hundred thirty-eight million, three hundred fifty-five thousand, nine hundred eighty-one".