139384781 has 4 divisors (see below), whose sum is σ = 139437312. Its totient is φ = 139332252.

The previous prime is 139384697. The next prime is 139384799. The reversal of 139384781 is 187483931.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4, and also an emirpimes, since its reverse is a distinct semiprime: 187483931 = 491 ⋅381841.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-139384781 is a prime.

It is a super-2 number, since 2×139384781² = 38856234348835922, 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 (139384081) 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, 22061 + ... + 27666.

It is an arithmetic number, because the mean of its divisors is an integer number (34859328).

Almost surely, 2^139384781 is an apocalyptic number.

It is an amenable number.

139384781 is a deficient number, since it is larger than the sum of its proper divisors (52531).

139384781 is an equidigital number, since it uses as much as digits as its factorization.

139384781 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 52530.

The product of its digits is 145152, while the sum is 44.

The square root of 139384781 is about 11806.1331942343. The cubic root of 139384781 is about 518.4876930795.

The spelling of 139384781 in words is "one hundred thirty-nine million, three hundred eighty-four thousand, seven hundred eighty-one".