139308781 has 4 divisors (see below), whose sum is σ = 140745052. Its totient is φ = 137872512.

The previous prime is 139308739. The next prime is 139308787. The reversal of 139308781 is 187803931.

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

It can be written as a sum of positive squares in 2 ways, for example, as 111112681 + 28196100 = 10541^2 + 5310^2 .

It is a cyclic number.

It is not a de Polignac number, because 139308781 - 2⁹ = 139308269 is a prime.

It is a super-2 number, since 2×139308781² = 38813872927411922, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (139308787) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 717990 + ... + 718183.

It is an arithmetic number, because the mean of its divisors is an integer number (35186263).

Almost surely, 2^139308781 is an apocalyptic number.

It is an amenable number.

139308781 is a deficient number, since it is larger than the sum of its proper divisors (1436271).

139308781 is an equidigital number, since it uses as much as digits as its factorization.

139308781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1436270.

The product of its (nonzero) digits is 36288, while the sum is 40.

The square root of 139308781 is about 11802.9140893256. The cubic root of 139308781 is about 518.3934402530.

The spelling of 139308781 in words is "one hundred thirty-nine million, three hundred eight thousand, seven hundred eighty-one".