388891021 has 2 divisors, whose sum is σ = 388891022. Its totient is φ = 388891020.

The previous prime is 388890967. The next prime is 388891039. The reversal of 388891021 is 120198883.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 384708996 + 4182025 = 19614^2 + 2045^2 .

It is a cyclic number.

It is not a de Polignac number, because 388891021 - 2¹³ = 388882829 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (388891121) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 194445510 + 194445511.

It is an arithmetic number, because the mean of its divisors is an integer number (194445511).

Almost surely, 2^388891021 is an apocalyptic number.

It is an amenable number.

388891021 is a deficient number, since it is larger than the sum of its proper divisors (1).

388891021 is an equidigital number, since it uses as much as digits as its factorization.

388891021 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 27648, while the sum is 40.

The square root of 388891021 is about 19720.3200024746. The cubic root of 388891021 is about 729.9211905915.

The spelling of 388891021 in words is "three hundred eighty-eight million, eight hundred ninety-one thousand, twenty-one".