665139971 has 2 divisors, whose sum is σ = 665139972. Its totient is φ = 665139970.

The previous prime is 665139899. The next prime is 665139989. The reversal of 665139971 is 179931566.

It is a happy number.

665139971 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 665139971 - 2²² = 660945667 is a prime.

It is a super-2 number, since 2×665139971² = 884822362043761682, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (665139991) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 332569985 + 332569986.

It is an arithmetic number, because the mean of its divisors is an integer number (332569986).

Almost surely, 2^665139971 is an apocalyptic number.

665139971 is a deficient number, since it is larger than the sum of its proper divisors (1).

665139971 is an equidigital number, since it uses as much as digits as its factorization.

665139971 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 306180, while the sum is 47.

The square root of 665139971 is about 25790.3076949462. The cubic root of 665139971 is about 872.9131092974.

The spelling of 665139971 in words is "six hundred sixty-five million, one hundred thirty-nine thousand, nine hundred seventy-one".