66817640 has 48 divisors (see below), whose sum is σ = 153146700. Its totient is φ = 26233856.

The previous prime is 66817637. The next prime is 66817649. The reversal of 66817640 is 4671866.

It can be written as a sum of positive squares in 6 ways, for example, as 23600164 + 43217476 = 4858^2 + 6574^2 .

It is a junction number, because it is equal to n+sod(n) for n = 66817594 and 66817603.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66817649) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 487652 + ... + 487788.

Almost surely, 2^66817640 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 66817640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (76573350).

66817640 is an abundant number, since it is smaller than the sum of its proper divisors (86329060).

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

66817640 is a wasteful number, since it uses less digits than its factorization.

66817640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 374 (or 233 counting only the distinct ones).

The product of its (nonzero) digits is 48384, while the sum is 38.

The square root of 66817640 is about 8174.2057718166. The cubic root of 66817640 is about 405.7859857127.

The spelling of 66817640 in words is "sixty-six million, eight hundred seventeen thousand, six hundred forty".