138648781 has 4 divisors (see below), whose sum is σ = 139944672. Its totient is φ = 137352892.

The previous prime is 138648779. The next prime is 138648817. The reversal of 138648781 is 187846831.

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.

It is a cyclic number.

It is not a de Polignac number, because 138648781 - 2¹ = 138648779 is a prime.

It is a super-2 number, since 2×138648781² = 38446968945571922, 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 (138648701) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 647785 + ... + 647998.

It is an arithmetic number, because the mean of its divisors is an integer number (34986168).

Almost surely, 2^138648781 is an apocalyptic number.

It is an amenable number.

138648781 is a deficient number, since it is larger than the sum of its proper divisors (1295891).

138648781 is a wasteful number, since it uses less digits than its factorization.

138648781 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1295890.

The product of its digits is 258048, while the sum is 46.

The square root of 138648781 is about 11774.9216982535. The cubic root of 138648781 is about 517.5734837733.

The spelling of 138648781 in words is "one hundred thirty-eight million, six hundred forty-eight thousand, seven hundred eighty-one".