66285991 has 4 divisors (see below), whose sum is σ = 66311392. Its totient is φ = 66260592.

The previous prime is 66285983. The next prime is 66286037. The reversal of 66285991 is 19958266.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 66285991 - 2³ = 66285983 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66289991) 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 in 3 ways as a sum of consecutive naturals, for example, 8271 + ... + 14176.

It is an arithmetic number, because the mean of its divisors is an integer number (16577848).

Almost surely, 2^66285991 is an apocalyptic number.

66285991 is a deficient number, since it is larger than the sum of its proper divisors (25401).

66285991 is a wasteful number, since it uses less digits than its factorization.

66285991 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 25400.

The product of its digits is 233280, while the sum is 46.

The square root of 66285991 is about 8141.6209074115. The cubic root of 66285991 is about 404.7068772672.

It can be divided in two parts, 66285 and 991, that added together give a palindrome (67276).

The spelling of 66285991 in words is "sixty-six million, two hundred eighty-five thousand, nine hundred ninety-one".