66656240 has 80 divisors (see below), whose sum is σ = 181958592. Its totient is φ = 22228992.

The previous prime is 66656209. The next prime is 66656243. The reversal of 66656240 is 4265666.

It is a tau number, because it is divible by the number of its divisors (80).

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 66656240.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66656243) 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, 19112 + ... + 22328.

Almost surely, 2^66656240 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 66656240, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (90979296).

66656240 is an abundant number, since it is smaller than the sum of its proper divisors (115302352).

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

66656240 is a wasteful number, since it uses less digits than its factorization.

66656240 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3274 (or 3268 counting only the distinct ones).

The product of its (nonzero) digits is 51840, while the sum is 35.

The square root of 66656240 is about 8164.3272839837. The cubic root of 66656240 is about 405.4589929051.

The spelling of 66656240 in words is "sixty-six million, six hundred fifty-six thousand, two hundred forty".