65671991 has 16 divisors (see below), whose sum is σ = 82199040. Its totient is φ = 50971680.

The previous prime is 65671987. The next prime is 65671997. The reversal of 65671991 is 19917656.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 65671991 - 2² = 65671987 is a prime.

It is a Smith number, since the sum of its digits (44) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (65671997) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 19790 + ... + 22868.

It is an arithmetic number, because the mean of its divisors is an integer number (5137440).

Almost surely, 2^65671991 is an apocalyptic number.

65671991 is a deficient number, since it is larger than the sum of its proper divisors (16527049).

65671991 is a wasteful number, since it uses less digits than its factorization.

65671991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3374.

The product of its digits is 102060, while the sum is 44.

The square root of 65671991 is about 8103.8257014820. The cubic root of 65671991 is about 403.4534136159.

It can be divided in two parts, 6567 and 1991, that added together give a palindrome (8558).

The spelling of 65671991 in words is "sixty-five million, six hundred seventy-one thousand, nine hundred ninety-one".