66991959 has 12 divisors (see below), whose sum is σ = 97506552. Its totient is φ = 44319600.

The previous prime is 66991949. The next prime is 66991973. The reversal of 66991959 is 95919966.

It is not a de Polignac number, because 66991959 - 2⁷ = 66991831 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66991949) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 27232 + ... + 29589.

It is an arithmetic number, because the mean of its divisors is an integer number (8125546).

Almost surely, 2^66991959 is an apocalyptic number.

66991959 is a deficient number, since it is larger than the sum of its proper divisors (30514593).

66991959 is a wasteful number, since it uses less digits than its factorization.

66991959 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 56958 (or 56955 counting only the distinct ones).

The product of its digits is 1180980, while the sum is 54.

The square root of 66991959 is about 8184.8615748832. The cubic root of 66991959 is about 406.1385611814.

The spelling of 66991959 in words is "sixty-six million, nine hundred ninety-one thousand, nine hundred fifty-nine".