139691081 has 2 divisors, whose sum is σ = 139691082. Its totient is φ = 139691080.

The previous prime is 139691017. The next prime is 139691129. The reversal of 139691081 is 180196931.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 116985856 + 22705225 = 10816^2 + 4765^2 .

It is a cyclic number.

It is not a de Polignac number, because 139691081 - 2⁶ = 139691017 is a prime.

It is a super-2 number, since 2×139691081² = 39027196221897122, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (139691011) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69845540 + 69845541.

It is an arithmetic number, because the mean of its divisors is an integer number (69845541).

Almost surely, 2^139691081 is an apocalyptic number.

It is an amenable number.

139691081 is a deficient number, since it is larger than the sum of its proper divisors (1).

139691081 is an equidigital number, since it uses as much as digits as its factorization.

139691081 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 11664, while the sum is 38.

The square root of 139691081 is about 11819.0981466438. The cubic root of 139691081 is about 518.8672098626.

The spelling of 139691081 in words is "one hundred thirty-nine million, six hundred ninety-one thousand, eighty-one".