138828821 has 4 divisors (see below), whose sum is σ = 138856032. Its totient is φ = 138801612.

The previous prime is 138828803. The next prime is 138828827. The reversal of 138828821 is 128828831.

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 a de Polignac number, because none of the positive numbers 2^k-138828821 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138828827) 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, 3401 + ... + 17006.

It is an arithmetic number, because the mean of its divisors is an integer number (34714008).

It is a Poulet number, since it divides 2^138828820-1.

Almost surely, 2^138828821 is an apocalyptic number.

138828821 is the 6803-rd octagonal number.

It is an amenable number.

138828821 is a deficient number, since it is larger than the sum of its proper divisors (27211).

138828821 is an equidigital number, since it uses as much as digits as its factorization.

138828821 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 27210.

The product of its digits is 49152, while the sum is 41.

The square root of 138828821 is about 11782.5642794767. The cubic root of 138828821 is about 517.7974156014.

The spelling of 138828821 in words is "one hundred thirty-eight million, eight hundred twenty-eight thousand, eight hundred twenty-one".