138521881 has 2 divisors, whose sum is σ = 138521882. Its totient is φ = 138521880.

The previous prime is 138521869. The next prime is 138521891. The reversal of 138521881 is 188125831.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 92064025 + 46457856 = 9595^2 + 6816^2 .

It is a cyclic number.

It is not a de Polignac number, because 138521881 - 2⁵ = 138521849 is a prime.

It is a super-2 number, since 2×138521881² = 38376623031556322, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 138521881.

It is not a weakly prime, because it can be changed into another prime (138521891) 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 as a sum of consecutive naturals, namely, 69260940 + 69260941.

It is an arithmetic number, because the mean of its divisors is an integer number (69260941).

Almost surely, 2^138521881 is an apocalyptic number.

It is an amenable number.

138521881 is a deficient number, since it is larger than the sum of its proper divisors (1).

138521881 is an equidigital number, since it uses as much as digits as its factorization.

138521881 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15360, while the sum is 37.

The square root of 138521881 is about 11769.5318938350. The cubic root of 138521881 is about 517.4155304109.

The spelling of 138521881 in words is "one hundred thirty-eight million, five hundred twenty-one thousand, eight hundred eighty-one".