388928021 has 2 divisors, whose sum is σ = 388928022. Its totient is φ = 388928020.

The previous prime is 388928017. The next prime is 388928039. The reversal of 388928021 is 120829883.

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., 388641796 + 286225 = 19714^2 + 535^2 .

It is a cyclic number.

It is not a de Polignac number, because 388928021 - 2² = 388928017 is a prime.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 388928021.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (388928051) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 194464010 + 194464011.

It is an arithmetic number, because the mean of its divisors is an integer number (194464011).

Almost surely, 2^388928021 is an apocalyptic number.

It is an amenable number.

388928021 is a deficient number, since it is larger than the sum of its proper divisors (1).

388928021 is an equidigital number, since it uses as much as digits as its factorization.

388928021 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 55296, while the sum is 41.

The square root of 388928021 is about 19721.2580988131. The cubic root of 388928021 is about 729.9443386596.

The spelling of 388928021 in words is "three hundred eighty-eight million, nine hundred twenty-eight thousand, twenty-one".