66646404 has 144 divisors (see below), whose sum is σ = 194987520. Its totient is φ = 19008000.

The previous prime is 66646403. The next prime is 66646421. The reversal of 66646404 is 40464666.

It is a happy number.

It is a super-2 number, since 2×66646404² = 8883486332262432, which contains 22 as substring.

It is a Harshad number since it is a multiple of its sum of digits (36).

It is not an unprimeable number, because it can be changed into a prime (66646403) by changing a digit.

It is a polite number, since it can be written in 47 ways as a sum of consecutive naturals, for example, 748792 + ... + 748880.

It is an arithmetic number, because the mean of its divisors is an integer number (1354080).

Almost surely, 2^66646404 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 66646404, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (97493760).

66646404 is an abundant number, since it is smaller than the sum of its proper divisors (128341116).

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

66646404 is a wasteful number, since it uses less digits than its factorization.

66646404 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 202 (or 197 counting only the distinct ones).

The product of its (nonzero) digits is 82944, while the sum is 36.

The square root of 66646404 is about 8163.7248851244. The cubic root of 66646404 is about 405.4390483316.

The spelling of 66646404 in words is "sixty-six million, six hundred forty-six thousand, four hundred four".