139281991 has 2 divisors, whose sum is σ = 139281992. Its totient is φ = 139281990.

The previous prime is 139281973. The next prime is 139282001. The reversal of 139281991 is 199182931.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 139281991 - 2²⁷ = 5064263 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (139281941) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69640995 + 69640996.

It is an arithmetic number, because the mean of its divisors is an integer number (69640996).

Almost surely, 2^139281991 is an apocalyptic number.

139281991 is a deficient number, since it is larger than the sum of its proper divisors (1).

139281991 is an equidigital number, since it uses as much as digits as its factorization.

139281991 is an evil number, because the sum of its binary digits is even.

The product of its digits is 34992, while the sum is 43.

The square root of 139281991 is about 11801.7791455356. The cubic root of 139281991 is about 518.3602079602.

The spelling of 139281991 in words is "one hundred thirty-nine million, two hundred eighty-one thousand, nine hundred ninety-one".