388405921 has 2 divisors, whose sum is σ = 388405922. Its totient is φ = 388405920.

The previous prime is 388405907. The next prime is 388405931. The reversal of 388405921 is 129504883.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 315559696 + 72846225 = 17764^2 + 8535^2 .

It is a cyclic number.

It is not a de Polignac number, because 388405921 - 2¹⁹ = 387881633 is a prime.

It is not a weakly prime, because it can be changed into another prime (388405931) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 194202960 + 194202961.

It is an arithmetic number, because the mean of its divisors is an integer number (194202961).

Almost surely, 2^388405921 is an apocalyptic number.

It is an amenable number.

388405921 is a deficient number, since it is larger than the sum of its proper divisors (1).

388405921 is an equidigital number, since it uses as much as digits as its factorization.

388405921 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 69120, while the sum is 40.

The square root of 388405921 is about 19708.0166683510. The cubic root of 388405921 is about 729.6175647424.

The spelling of 388405921 in words is "three hundred eighty-eight million, four hundred five thousand, nine hundred twenty-one".