66815970 has 128 divisors (see below), whose sum is σ = 185794560. Its totient is φ = 15240960.

The previous prime is 66815953. The next prime is 66815977. The reversal of 66815970 is 7951866.

It is a Smith number, since the sum of its digits (42) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is not an unprimeable number, because it can be changed into a prime (66815977) 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 63 ways as a sum of consecutive naturals, for example, 526047 + ... + 526173.

It is an arithmetic number, because the mean of its divisors is an integer number (1451520).

Almost surely, 2^66815970 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66815970, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (92897280).

66815970 is an abundant number, since it is smaller than the sum of its proper divisors (118978590).

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

66815970 is a wasteful number, since it uses less digits than its factorization.

66815970 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 240.

The product of its (nonzero) digits is 90720, while the sum is 42.

The square root of 66815970 is about 8174.1036205813. The cubic root of 66815970 is about 405.7826050274.

The spelling of 66815970 in words is "sixty-six million, eight hundred fifteen thousand, nine hundred seventy".