138726521 has 2 divisors, whose sum is σ = 138726522. Its totient is φ = 138726520.

The previous prime is 138726503. The next prime is 138726551. The reversal of 138726521 is 125627831.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 121793296 + 16933225 = 11036^2 + 4115^2 .

It is a cyclic number.

It is not a de Polignac number, because 138726521 - 2¹⁰ = 138725497 is a prime.

It is not a weakly prime, because it can be changed into another prime (138726551) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69363260 + 69363261.

It is an arithmetic number, because the mean of its divisors is an integer number (69363261).

Almost surely, 2^138726521 is an apocalyptic number.

It is an amenable number.

138726521 is a deficient number, since it is larger than the sum of its proper divisors (1).

138726521 is an equidigital number, since it uses as much as digits as its factorization.

138726521 is an evil number, because the sum of its binary digits is even.

The product of its digits is 20160, while the sum is 35.

The square root of 138726521 is about 11778.2223191787. Note that the first 3 decimals coincide. The cubic root of 138726521 is about 517.6701997213.

The spelling of 138726521 in words is "one hundred thirty-eight million, seven hundred twenty-six thousand, five hundred twenty-one".