138891491 has 2 divisors, whose sum is σ = 138891492. Its totient is φ = 138891490.

The previous prime is 138891481. The next prime is 138891497. The reversal of 138891491 is 194198831.

It is a strong prime.

It is an emirp because it is prime and its reverse (194198831) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 138891491 - 2⁶ = 138891427 is a prime.

It is a super-3 number, since 3×138891491³ (a number of 25 digits) contains 333 as substring.

It is not a weakly prime, because it can be changed into another prime (138891497) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69445745 + 69445746.

It is an arithmetic number, because the mean of its divisors is an integer number (69445746).

Almost surely, 2^138891491 is an apocalyptic number.

138891491 is a deficient number, since it is larger than the sum of its proper divisors (1).

138891491 is an equidigital number, since it uses as much as digits as its factorization.

138891491 is an evil number, because the sum of its binary digits is even.

The product of its digits is 62208, while the sum is 44.

The square root of 138891491 is about 11785.2234174834. The cubic root of 138891491 is about 517.8753184511.

The spelling of 138891491 in words is "one hundred thirty-eight million, eight hundred ninety-one thousand, four hundred ninety-one".