388690921 has 4 divisors (see below), whose sum is σ = 390726144. Its totient is φ = 386655700.

The previous prime is 388690903. The next prime is 388690933. The reversal of 388690921 is 129096883.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 388690921 - 2⁷ = 388690793 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (388690021) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 1017325 + ... + 1017706.

It is an arithmetic number, because the mean of its divisors is an integer number (97681536).

Almost surely, 2^388690921 is an apocalyptic number.

It is an amenable number.

388690921 is a deficient number, since it is larger than the sum of its proper divisors (2035223).

388690921 is a wasteful number, since it uses less digits than its factorization.

388690921 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2035222.

The product of its (nonzero) digits is 186624, while the sum is 46.

The square root of 388690921 is about 19715.2459026004. The cubic root of 388690921 is about 729.7959778881.

The spelling of 388690921 in words is "three hundred eighty-eight million, six hundred ninety thousand, nine hundred twenty-one".