66511856 has 40 divisors (see below), whose sum is σ = 136724880. Its totient is φ = 31256064.

The previous prime is 66511843. The next prime is 66511859. The reversal of 66511856 is 65811566.

It is a Harshad number since it is a multiple of its sum of digits (38).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66511859) by changing a digit.

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, 40850 + ... + 42446.

It is an arithmetic number, because the mean of its divisors is an integer number (3418122).

Almost surely, 2^66511856 is an apocalyptic number.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66511856, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (68362440).

66511856 is an abundant number, since it is smaller than the sum of its proper divisors (70213024).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

66511856 is a wasteful number, since it uses less digits than its factorization.

66511856 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1761 (or 1755 counting only the distinct ones).

The product of its digits is 43200, while the sum is 38.

The square root of 66511856 is about 8155.4801207532. The cubic root of 66511856 is about 405.1660265288.

It can be divided in two parts, 665 and 11856, that added together give a palindrome (12521).

The spelling of 66511856 in words is "sixty-six million, five hundred eleven thousand, eight hundred fifty-six".