664771440 has 160 divisors (see below), whose sum is σ = 2142720000. Its totient is φ = 170311680.

The previous prime is 664771439. The next prime is 664771447. The reversal of 664771440 is 44177466.

It is a happy number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (664771447) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 1480336 + ... + 1480784.

It is an arithmetic number, because the mean of its divisors is an integer number (13392000).

Almost surely, 2^664771440 is an apocalyptic number.

664771440 is a gapful number since it is divisible by the number (60) 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 664771440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1071360000).

664771440 is an abundant number, since it is smaller than the sum of its proper divisors (1477948560).

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

664771440 is a wasteful number, since it uses less digits than its factorization.

664771440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 695 (or 689 counting only the distinct ones).

The product of its (nonzero) digits is 112896, while the sum is 39.

The square root of 664771440 is about 25783.1619472864. The cubic root of 664771440 is about 872.7518625489.

It can be divided in two parts, 6647 and 71440, that added together give a palindrome (78087).

The spelling of 664771440 in words is "six hundred sixty-four million, seven hundred seventy-one thousand, four hundred forty".