66431664 has 100 divisors (see below), whose sum is σ = 207115216. Its totient is φ = 20435328.

The previous prime is 66431611. The next prime is 66431669. The reversal of 66431664 is 46613466.

66431664 is a `hidden beast` number, since 6 + 643 + 1 + 6 + 6 + 4 = 666.

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

It is a nude number because it is divisible by every one of its digits.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66431669) by changing a digit.

It is a polite number, since it can be written in 19 ways as a sum of consecutive naturals, for example, 14877 + ... + 18819.

Almost surely, 2^66431664 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 66431664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (103557608).

66431664 is an abundant number, since it is smaller than the sum of its proper divisors (140683552).

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

66431664 is a wasteful number, since it uses less digits than its factorization.

66431664 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 3976 (or 3961 counting only the distinct ones).

The product of its digits is 62208, while the sum is 36.

The square root of 66431664 is about 8150.5621891990. The cubic root of 66431664 is about 405.0031275479.

The spelling of 66431664 in words is "sixty-six million, four hundred thirty-one thousand, six hundred sixty-four".