138691481 has 2 divisors, whose sum is σ = 138691482. Its totient is φ = 138691480.

The previous prime is 138691453. The next prime is 138691499. The reversal of 138691481 is 184196831.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 136515856 + 2175625 = 11684^2 + 1475^2 .

It is a cyclic number.

It is not a de Polignac number, because 138691481 - 2¹⁰ = 138690457 is a prime.

It is a super-2 number, since 2×138691481² = 38470653803946722, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (138691181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69345740 + 69345741.

It is an arithmetic number, because the mean of its divisors is an integer number (69345741).

Almost surely, 2^138691481 is an apocalyptic number.

It is an amenable number.

138691481 is a deficient number, since it is larger than the sum of its proper divisors (1).

138691481 is an equidigital number, since it uses as much as digits as its factorization.

138691481 is an evil number, because the sum of its binary digits is even.

The product of its digits is 41472, while the sum is 41.

The square root of 138691481 is about 11776.7347342122. The cubic root of 138691481 is about 517.6266111051.

The spelling of 138691481 in words is "one hundred thirty-eight million, six hundred ninety-one thousand, four hundred eighty-one".