66815910 has 144 divisors (see below), whose sum is σ = 205405200. Its totient is φ = 15023232.

The previous prime is 66815873. The next prime is 66815911. The reversal of 66815910 is 1951866.

66815910 is a `hidden beast` number, since 6 + 68 + 1 + 591 + 0 = 666.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66815911) 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 71 ways as a sum of consecutive naturals, for example, 480621 + ... + 480759.

It is an arithmetic number, because the mean of its divisors is an integer number (1426425).

Almost surely, 2^66815910 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66815910, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (102702600).

66815910 is an abundant number, since it is smaller than the sum of its proper divisors (138589290).

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

66815910 is a wasteful number, since it uses less digits than its factorization.

66815910 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 275 (or 265 counting only the distinct ones).

The product of its (nonzero) digits is 12960, while the sum is 36.

The square root of 66815910 is about 8174.0999504533. The cubic root of 66815910 is about 405.7824835646.

The spelling of 66815910 in words is "sixty-six million, eight hundred fifteen thousand, nine hundred ten".