81790139 has 4 divisors (see below), whose sum is σ = 85346256. Its totient is φ = 78234024.

The previous prime is 81790133. The next prime is 81790147. The reversal of 81790139 is 93109718.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-81790139 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (81790133) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1778024 + ... + 1778069.

It is an arithmetic number, because the mean of its divisors is an integer number (21336564).

Almost surely, 2^81790139 is an apocalyptic number.

81790139 is a deficient number, since it is larger than the sum of its proper divisors (3556117).

81790139 is a wasteful number, since it uses less digits than its factorization.

81790139 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3556116.

The product of its (nonzero) digits is 13608, while the sum is 38.

The square root of 81790139 is about 9043.7900793860. The cubic root of 81790139 is about 434.0772070590.

The spelling of 81790139 in words is "eighty-one million, seven hundred ninety thousand, one hundred thirty-nine".