139391081 has 4 divisors (see below), whose sum is σ = 144197700. Its totient is φ = 134584464.

The previous prime is 139391071. The next prime is 139391089. The reversal of 139391081 is 180193931.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 180193931 = 17 ⋅10599643.

It can be written as a sum of positive squares in 2 ways, for example, as 89208025 + 50183056 = 9445^2 + 7084^2 .

It is a cyclic number.

It is not a de Polignac number, because 139391081 - 2¹⁸ = 139128937 is a prime.

It is a super-2 number, since 2×139391081² = 38859746924697122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (139391089) 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 in 3 ways as a sum of consecutive naturals, for example, 2403266 + ... + 2403323.

It is an arithmetic number, because the mean of its divisors is an integer number (36049425).

Almost surely, 2^139391081 is an apocalyptic number.

It is an amenable number.

139391081 is a deficient number, since it is larger than the sum of its proper divisors (4806619).

139391081 is an equidigital number, since it uses as much as digits as its factorization.

139391081 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4806618.

The product of its (nonzero) digits is 5832, while the sum is 35.

The square root of 139391081 is about 11806.4000016940. The cubic root of 139391081 is about 518.4955046049.

The spelling of 139391081 in words is "one hundred thirty-nine million, three hundred ninety-one thousand, eighty-one".