138945981 has 16 divisors (see below), whose sum is σ = 196401024. Its totient is φ = 87074304.

The previous prime is 138945971. The next prime is 138945997. The reversal of 138945981 is 189549831.

It is not a de Polignac number, because 138945981 - 2¹⁵ = 138913213 is a prime.

It is a super-2 number, since 2×138945981² = 38611971272104722, which contains 22 as substring.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 138945981.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138945941) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 68721 + ... + 70713.

It is an arithmetic number, because the mean of its divisors is an integer number (12275064).

Almost surely, 2^138945981 is an apocalyptic number.

It is an amenable number.

138945981 is a deficient number, since it is larger than the sum of its proper divisors (57455043).

138945981 is a wasteful number, since it uses less digits than its factorization.

138945981 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3380.

The product of its digits is 311040, while the sum is 48.

The square root of 138945981 is about 11787.5349840414. The cubic root of 138945981 is about 517.9430339903.

The spelling of 138945981 in words is "one hundred thirty-eight million, nine hundred forty-five thousand, nine hundred eighty-one".