138643961 has 4 divisors (see below), whose sum is σ = 138943872. Its totient is φ = 138344052.

The previous prime is 138643957. The next prime is 138643987. The reversal of 138643961 is 169346831.

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 138643961 - 2² = 138643957 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (138643991) 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, 149261 + ... + 150186.

It is an arithmetic number, because the mean of its divisors is an integer number (34735968).

Almost surely, 2^138643961 is an apocalyptic number.

It is an amenable number.

138643961 is a deficient number, since it is larger than the sum of its proper divisors (299911).

138643961 is an equidigital number, since it uses as much as digits as its factorization.

138643961 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 299910.

The product of its digits is 93312, while the sum is 41.

The square root of 138643961 is about 11774.7170242006. The cubic root of 138643961 is about 517.5674860452.

The spelling of 138643961 in words is "one hundred thirty-eight million, six hundred forty-three thousand, nine hundred sixty-one".