66191881 has 16 divisors (see below), whose sum is σ = 77051520. Its totient is φ = 55693440.

The previous prime is 66191837. The next prime is 66191903. The reversal of 66191881 is 18819166.

It is a cyclic number.

It is not a de Polignac number, because 66191881 - 2¹⁵ = 66159113 is a prime.

It is a super-2 number, since 2×66191881² = 8762730220636322, which contains 22 as substring.

Its product of digits (20736) is a multiple of the sum of its prime divisors (864).

It is not an unprimeable number, because it can be changed into a prime (66191821) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 112470 + ... + 113056.

It is an arithmetic number, because the mean of its divisors is an integer number (4815720).

Almost surely, 2^66191881 is an apocalyptic number.

It is an amenable number.

66191881 is a deficient number, since it is larger than the sum of its proper divisors (10859639).

66191881 is a wasteful number, since it uses less digits than its factorization.

66191881 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 864.

The product of its digits is 20736, while the sum is 40.

The square root of 66191881 is about 8135.8392929064. The cubic root of 66191881 is about 404.5152580798.

The spelling of 66191881 in words is "sixty-six million, one hundred ninety-one thousand, eight hundred eighty-one".