66991894 has 16 divisors (see below), whose sum is σ = 102649680. Its totient is φ = 32778720.

The previous prime is 66991877. The next prime is 66991907. The reversal of 66991894 is 49819966.

It is a congruent number.

It is an unprimeable number.

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 7 ways as a sum of consecutive naturals, for example, 65104 + ... + 66124.

It is an arithmetic number, because the mean of its divisors is an integer number (6415605).

Almost surely, 2^66991894 is an apocalyptic number.

66991894 is a deficient number, since it is larger than the sum of its proper divisors (35657786).

66991894 is a wasteful number, since it uses less digits than its factorization.

66991894 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1695.

The product of its digits is 839808, while the sum is 52.

The square root of 66991894 is about 8184.8576041370. The cubic root of 66991894 is about 406.1384298273.

The spelling of 66991894 in words is "sixty-six million, nine hundred ninety-one thousand, eight hundred ninety-four".