66666491 has 4 divisors (see below), whose sum is σ = 67191552. Its totient is φ = 66141432.

The previous prime is 66666487. The next prime is 66666493. The reversal of 66666491 is 19466666.

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 66666491 - 2² = 66666487 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (66666493) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 262340 + ... + 262593.

It is an arithmetic number, because the mean of its divisors is an integer number (16797888).

Almost surely, 2^66666491 is an apocalyptic number.

66666491 is a deficient number, since it is larger than the sum of its proper divisors (525061).

66666491 is a wasteful number, since it uses less digits than its factorization.

66666491 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 525060.

The product of its digits is 279936, while the sum is 44.

The square root of 66666491 is about 8164.9550519277. The cubic root of 66666491 is about 405.4797768912.

The spelling of 66666491 in words is "sixty-six million, six hundred sixty-six thousand, four hundred ninety-one".