66400664 has 32 divisors (see below), whose sum is σ = 137471040. Its totient is φ = 29815200.

The previous prime is 66400661. The next prime is 66400751. The reversal of 66400664 is 46600466.

It is a happy number.

It is a self number, because there is not a number n which added to its sum of digits gives 66400664.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (66400661) 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, 2759 + ... + 11849.

It is an arithmetic number, because the mean of its divisors is an integer number (4295970).

Almost surely, 2^66400664 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 66400664, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (68735520).

66400664 is an abundant number, since it is smaller than the sum of its proper divisors (71070376).

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

66400664 is a wasteful number, since it uses less digits than its factorization.

66400664 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9191 (or 9187 counting only the distinct ones).

The product of its (nonzero) digits is 20736, while the sum is 32.

The square root of 66400664 is about 8148.6602579811. The cubic root of 66400664 is about 404.9401201925.

It can be divided in two parts, 66400 and 664, that multiplied together give a square (44089600 = 6640²).

The spelling of 66400664 in words is "sixty-six million, four hundred thousand, six hundred sixty-four".