66521688 has 64 divisors (see below), whose sum is σ = 172698240. Its totient is φ = 21337344.

The previous prime is 66521683. The next prime is 66521699. The reversal of 66521688 is 88612566.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66521683) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 74895 + ... + 75777.

It is an arithmetic number, because the mean of its divisors is an integer number (2698410).

Almost surely, 2^66521688 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 66521688, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (86349120).

66521688 is an abundant number, since it is smaller than the sum of its proper divisors (106176552).

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

66521688 is a wasteful number, since it uses less digits than its factorization.

66521688 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1008 (or 1004 counting only the distinct ones).

The product of its digits is 138240, while the sum is 42.

The square root of 66521688 is about 8156.0828833454. The cubic root of 66521688 is about 405.1859898674.

The spelling of 66521688 in words is "sixty-six million, five hundred twenty-one thousand, six hundred eighty-eight".