388139021 has 2 divisors, whose sum is σ = 388139022. Its totient is φ = 388139020.

The previous prime is 388138997. The next prime is 388139033. The reversal of 388139021 is 120931883.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 212284900 + 175854121 = 14570^2 + 13261^2 .

It is an emirp because it is prime and its reverse (120931883) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 388139021 - 2⁶ = 388138957 is a prime.

It is a Sophie Germain prime.

It is a Chen 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 (388139041) 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, 194069510 + 194069511.

It is an arithmetic number, because the mean of its divisors is an integer number (194069511).

Almost surely, 2^388139021 is an apocalyptic number.

It is an amenable number.

388139021 is a deficient number, since it is larger than the sum of its proper divisors (1).

388139021 is an equidigital number, since it uses as much as digits as its factorization.

388139021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 10368, while the sum is 35.

The square root of 388139021 is about 19701.2441485303. The cubic root of 388139021 is about 729.4504032414.

The spelling of 388139021 in words is "three hundred eighty-eight million, one hundred thirty-nine thousand, twenty-one".