66706640 has 320 divisors, whose sum is σ = 224985600. Its totient is φ = 18063360.

The previous prime is 66706621. The next prime is 66706643. The reversal of 66706640 is 4660766.

It is a Harshad number since it is a multiple of its sum of digits (35).

It is a self number, because there is not a number n which added to its sum of digits gives 66706640.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66706643) by changing a digit.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 3923912 + ... + 3923928.

It is an arithmetic number, because the mean of its divisors is an integer number (703080).

Almost surely, 2^66706640 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 66706640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (112492800).

66706640 is an abundant number, since it is smaller than the sum of its proper divisors (158278960).

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

66706640 is a wasteful number, since it uses less digits than its factorization.

66706640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75 (or 55 counting only the distinct ones).

The product of its (nonzero) digits is 36288, while the sum is 35.

The square root of 66706640 is about 8167.4132992031. The cubic root of 66706640 is about 405.5611588086.

The spelling of 66706640 in words is "sixty-six million, seven hundred six thousand, six hundred forty".