138787991 has 2 divisors, whose sum is σ = 138787992. Its totient is φ = 138787990.

The previous prime is 138787933. The next prime is 138788029. The reversal of 138787991 is 199787831.

138787991 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 138787991 - 2⁶ = 138787927 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (138787921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69393995 + 69393996.

It is an arithmetic number, because the mean of its divisors is an integer number (69393996).

Almost surely, 2^138787991 is an apocalyptic number.

138787991 is a deficient number, since it is larger than the sum of its proper divisors (1).

138787991 is an equidigital number, since it uses as much as digits as its factorization.

138787991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 762048, while the sum is 53.

The square root of 138787991 is about 11780.8315071560. The cubic root of 138787991 is about 517.7466486658.

The spelling of 138787991 in words is "one hundred thirty-eight million, seven hundred eighty-seven thousand, nine hundred ninety-one".