66491904 has 80 divisors (see below), whose sum is σ = 179867952. Its totient is φ = 21823488.

The previous prime is 66491903. The next prime is 66491917. The reversal of 66491904 is 40919466.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66491903) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 111832 + ... + 112424.

Almost surely, 2^66491904 is an apocalyptic number.

66491904 is a gapful number since it is divisible by the number (64) 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 66491904, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (89933976).

66491904 is an abundant number, since it is smaller than the sum of its proper divisors (113376048).

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

66491904 is an equidigital number, since it uses as much as digits as its factorization.

66491904 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 687 (or 671 counting only the distinct ones).

The product of its (nonzero) digits is 46656, while the sum is 39.

The square root of 66491904 is about 8154.2568024315. The cubic root of 66491904 is about 405.1255090356.

The spelling of 66491904 in words is "sixty-six million, four hundred ninety-one thousand, nine hundred four".