628943981 has 2 divisors, whose sum is σ = 628943982. Its totient is φ = 628943980.

The previous prime is 628943971. The next prime is 628944047. The reversal of 628943981 is 189349826.

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., 628755625 + 188356 = 25075^2 + 434^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-628943981 is a prime.

It is a super-2 number, since 2×628943981² = 791141062472256722, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (628943921) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 314471990 + 314471991.

It is an arithmetic number, because the mean of its divisors is an integer number (314471991).

Almost surely, 2^628943981 is an apocalyptic number.

It is an amenable number.

628943981 is a deficient number, since it is larger than the sum of its proper divisors (1).

628943981 is an equidigital number, since it uses as much as digits as its factorization.

628943981 is an evil number, because the sum of its binary digits is even.

The product of its digits is 746496, while the sum is 50.

The square root of 628943981 is about 25078.7555712001. The cubic root of 628943981 is about 856.7826336639.

The spelling of 628943981 in words is "six hundred twenty-eight million, nine hundred forty-three thousand, nine hundred eighty-one".