628666391 has 4 divisors (see below), whose sum is σ = 648945984. Its totient is φ = 608386800.

The previous prime is 628666369. The next prime is 628666393. The reversal of 628666391 is 193666826.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 628666391 - 2⁶ = 628666327 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (628666393) 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, 10139750 + ... + 10139811.

It is an arithmetic number, because the mean of its divisors is an integer number (162236496).

Almost surely, 2^628666391 is an apocalyptic number.

628666391 is a deficient number, since it is larger than the sum of its proper divisors (20279593).

628666391 is a wasteful number, since it uses less digits than its factorization.

628666391 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 20279592.

The product of its digits is 559872, while the sum is 47.

The square root of 628666391 is about 25073.2205948897. The cubic root of 628666391 is about 856.6565655788.

The spelling of 628666391 in words is "six hundred twenty-eight million, six hundred sixty-six thousand, three hundred ninety-one".