391217128 has 16 divisors (see below), whose sum is σ = 734086980. Its totient is φ = 195460608.

The previous prime is 391217111. The next prime is 391217129. The reversal of 391217128 is 821712193.

It can be written as a sum of positive squares in 2 ways, for example, as 363359844 + 27857284 = 19062^2 + 5278^2 .

It is a junction number, because it is equal to n+sod(n) for n = 391217093 and 391217102.

It is not an unprimeable number, because it can be changed into a prime (391217129) 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, 6825 + ... + 28792.

Almost surely, 2^391217128 is an apocalyptic number.

It is an amenable number.

391217128 is a deficient number, since it is larger than the sum of its proper divisors (342869852).

391217128 is a wasteful number, since it uses less digits than its factorization.

391217128 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 36996 (or 36992 counting only the distinct ones).

The product of its digits is 6048, while the sum is 34.

The square root of 391217128 is about 19779.2094887536. The cubic root of 391217128 is about 731.3736118692.

The spelling of 391217128 in words is "three hundred ninety-one million, two hundred seventeen thousand, one hundred twenty-eight".