664168638 has 48 divisors (see below), whose sum is σ = 1549875600. Its totient is φ = 189189504.

The previous prime is 664168633. The next prime is 664168651. The reversal of 664168638 is 836861466.

It is a super-2 number, since 2×664168638² = 882239959405550088, which contains 22 as substring.

It is a hoax number, since the sum of its digits (48) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664168633) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 99370 + ... + 105842.

It is an arithmetic number, because the mean of its divisors is an integer number (32289075).

Almost surely, 2^664168638 is an apocalyptic number.

It is a practical number, because each smaller number is the sum of distinct divisors of 664168638, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (774937800).

664168638 is an abundant number, since it is smaller than the sum of its proper divisors (885706962).

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

664168638 is a wasteful number, since it uses less digits than its factorization.

664168638 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6841 (or 6834 counting only the distinct ones).

The product of its digits is 995328, while the sum is 48.

The square root of 664168638 is about 25771.4694575222. The cubic root of 664168638 is about 872.4879845528.

The spelling of 664168638 in words is "six hundred sixty-four million, one hundred sixty-eight thousand, six hundred thirty-eight".