138161821 has 6 divisors (see below), whose sum is σ = 160718910. Its totient is φ = 118424376.

The previous prime is 138161819. The next prime is 138161827. The reversal of 138161821 is 128161831.

138161821 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It can be written as a sum of positive squares in only one way, i.e., 127012900 + 11148921 = 11270^2 + 3339^2 .

It is not a de Polignac number, because 138161821 - 2¹ = 138161819 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 (138161827) 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, 1409766 + ... + 1409863.

It is an arithmetic number, because the mean of its divisors is an integer number (26786485).

Almost surely, 2^138161821 is an apocalyptic number.

It is an amenable number.

138161821 is a deficient number, since it is larger than the sum of its proper divisors (22557089).

138161821 is an equidigital number, since it uses as much as digits as its factorization.

138161821 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2819643 (or 2819636 counting only the distinct ones).

The product of its digits is 2304, while the sum is 31.

The square root of 138161821 is about 11754.2256656915. The cubic root of 138161821 is about 516.9668352658.

The spelling of 138161821 in words is "one hundred thirty-eight million, one hundred sixty-one thousand, eight hundred twenty-one".