138534821 has 4 divisors (see below), whose sum is σ = 139252812. Its totient is φ = 137816832.

The previous prime is 138534817. The next prime is 138534839. The reversal of 138534821 is 128435831.

It is a happy number.

138534821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 128435831 = 983 ⋅130657.

It can be written as a sum of positive squares in 2 ways, for example, as 14546596 + 123988225 = 3814^2 + 11135^2 .

It is a cyclic number.

It is not a de Polignac number, because 138534821 - 2² = 138534817 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 (138533821) 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, 358706 + ... + 359091.

It is an arithmetic number, because the mean of its divisors is an integer number (34813203).

Almost surely, 2^138534821 is an apocalyptic number.

It is an amenable number.

138534821 is a deficient number, since it is larger than the sum of its proper divisors (717991).

138534821 is an equidigital number, since it uses as much as digits as its factorization.

138534821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 717990.

The product of its digits is 23040, while the sum is 35.

The square root of 138534821 is about 11770.0816054945. The cubic root of 138534821 is about 517.4316413398.

The spelling of 138534821 in words is "one hundred thirty-eight million, five hundred thirty-four thousand, eight hundred twenty-one".