138023821 has 6 divisors (see below), whose sum is σ = 149457930. Its totient is φ = 127406448.

The previous prime is 138023807. The next prime is 138023839. The reversal of 138023821 is 128320831.

It can be written as a sum of positive squares in 3 ways, for example, as 10017225 + 128006596 = 3165^2 + 11314^2 .

It is not a de Polignac number, because 138023821 - 2¹¹ = 138021773 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 138023821.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (138023891) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 408186 + ... + 408523.

It is an arithmetic number, because the mean of its divisors is an integer number (24909655).

Almost surely, 2^138023821 is an apocalyptic number.

It is an amenable number.

138023821 is a deficient number, since it is larger than the sum of its proper divisors (11434109).

138023821 is an equidigital number, since it uses as much as digits as its factorization.

138023821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 816735 (or 816722 counting only the distinct ones).

The product of its (nonzero) digits is 2304, while the sum is 28.

The square root of 138023821 is about 11748.3539698121. The cubic root of 138023821 is about 516.7946574805.

The spelling of 138023821 in words is "one hundred thirty-eight million, twenty-three thousand, eight hundred twenty-one".