66105991 has 8 divisors (see below), whose sum is σ = 76256640. Its totient is φ = 56132088.

The previous prime is 66105989. The next prime is 66106031. The reversal of 66105991 is 19950166.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 66105991 - 2¹ = 66105989 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 66105991.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66105961) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 43381 + ... + 44878.

It is an arithmetic number, because the mean of its divisors is an integer number (9532080).

Almost surely, 2^66105991 is an apocalyptic number.

66105991 is a deficient number, since it is larger than the sum of its proper divisors (10150649).

66105991 is a wasteful number, since it uses less digits than its factorization.

66105991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 88373.

The product of its (nonzero) digits is 14580, while the sum is 37.

The square root of 66105991 is about 8130.5590828675. The cubic root of 66105991 is about 404.3402172057.

The spelling of 66105991 in words is "sixty-six million, one hundred five thousand, nine hundred ninety-one".