128517931 has 2 divisors, whose sum is σ = 128517932. Its totient is φ = 128517930.

The previous prime is 128517929. The next prime is 128517953. The reversal of 128517931 is 139715821.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 128517931 - 2¹ = 128517929 is a prime.

It is a super-2 number, since 2×128517931² = 33033717177041522, which contains 22 as substring.

Together with 128517929, it forms a pair of twin primes.

It is equal to p_7298722 and since 128517931 and 7298722 have the same sum of digits, it is a Honaker prime.

It is not a weakly prime, because it can be changed into another prime (128517901) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 64258965 + 64258966.

It is an arithmetic number, because the mean of its divisors is an integer number (64258966).

Almost surely, 2^128517931 is an apocalyptic number.

128517931 is a deficient number, since it is larger than the sum of its proper divisors (1).

128517931 is an equidigital number, since it uses as much as digits as its factorization.

128517931 is an evil number, because the sum of its binary digits is even.

The product of its digits is 15120, while the sum is 37.

The square root of 128517931 is about 11336.5749236707. The cubic root of 128517931 is about 504.6472470351.

The spelling of 128517931 in words is "one hundred twenty-eight million, five hundred seventeen thousand, nine hundred thirty-one".