138858721 has 4 divisors (see below), whose sum is σ = 138900672. Its totient is φ = 138816772.

The previous prime is 138858691. The next prime is 138858749. The reversal of 138858721 is 127858831.

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 138858721 - 2⁵ = 138858689 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (138858791) 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, 15541 + ... + 22786.

It is an arithmetic number, because the mean of its divisors is an integer number (34725168).

Almost surely, 2^138858721 is an apocalyptic number.

It is an amenable number.

138858721 is a deficient number, since it is larger than the sum of its proper divisors (41951).

138858721 is an equidigital number, since it uses as much as digits as its factorization.

138858721 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 41950.

The product of its digits is 107520, while the sum is 43.

The square root of 138858721 is about 11783.8330351376. The cubic root of 138858721 is about 517.8345861525.

The spelling of 138858721 in words is "one hundred thirty-eight million, eight hundred fifty-eight thousand, seven hundred twenty-one".