66818640 has 160 divisors (see below), whose sum is σ = 244555776. Its totient is φ = 14768640.

The previous prime is 66818627. The next prime is 66818641. The reversal of 66818640 is 4681866.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66818641) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 51439 + ... + 52721.

Almost surely, 2^66818640 is an apocalyptic number.

66818640 is a gapful number since it is divisible by the number (60) formed by its first and last digit.

It is an amenable number.

It is a practical number, because each smaller number is the sum of distinct divisors of 66818640, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (122277888).

66818640 is an abundant number, since it is smaller than the sum of its proper divisors (177737136).

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

66818640 is a wasteful number, since it uses less digits than its factorization.

66818640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1337 (or 1331 counting only the distinct ones).

The product of its (nonzero) digits is 55296, while the sum is 39.

The square root of 66818640 is about 8174.2669396099. The cubic root of 66818640 is about 405.7880100482.

The spelling of 66818640 in words is "sixty-six million, eight hundred eighteen thousand, six hundred forty".