866139991 has 2 divisors, whose sum is σ = 866139992. Its totient is φ = 866139990.

The previous prime is 866139983. The next prime is 866140027. The reversal of 866139991 is 199931668.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 866139991 - 2³ = 866139983 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (866139931) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 433069995 + 433069996.

It is an arithmetic number, because the mean of its divisors is an integer number (433069996).

Almost surely, 2^866139991 is an apocalyptic number.

866139991 is a deficient number, since it is larger than the sum of its proper divisors (1).

866139991 is an equidigital number, since it uses as much as digits as its factorization.

866139991 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 629856, while the sum is 52.

The square root of 866139991 is about 29430.2563869226. The cubic root of 866139991 is about 953.2263309929.

The spelling of 866139991 in words is "eight hundred sixty-six million, one hundred thirty-nine thousand, nine hundred ninety-one".