138716621 has 2 divisors, whose sum is σ = 138716622. Its totient is φ = 138716620.

The previous prime is 138716609. The next prime is 138716671. The reversal of 138716621 is 126617831.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 137475625 + 1240996 = 11725^2 + 1114^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-138716621 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (138716671) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 69358310 + 69358311.

It is an arithmetic number, because the mean of its divisors is an integer number (69358311).

Almost surely, 2^138716621 is an apocalyptic number.

138716621 is the 6296-th centered heptagonal number.

It is an amenable number.

138716621 is a deficient number, since it is larger than the sum of its proper divisors (1).

138716621 is an equidigital number, since it uses as much as digits as its factorization.

138716621 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12096, while the sum is 35.

The square root of 138716621 is about 11777.8020445243. The cubic root of 138716621 is about 517.6578851885.

The spelling of 138716621 in words is "one hundred thirty-eight million, seven hundred sixteen thousand, six hundred twenty-one".