664979840 has 128 divisors (see below), whose sum is σ = 1830712320. Its totient is φ = 226252800.

The previous prime is 664979807. The next prime is 664979851. The reversal of 664979840 is 48979466.

It is a happy number.

It is a tau number, because it is divible by the number of its divisors (128).

It is a Smith number, since the sum of its digits (53) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 675989 + ... + 676971.

It is an arithmetic number, because the mean of its divisors is an integer number (14302440).

Almost surely, 2^664979840 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 664979840, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (915356160).

664979840 is an abundant number, since it is smaller than the sum of its proper divisors (1165732480).

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

664979840 is a wasteful number, since it uses less digits than its factorization.

664979840 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1160 (or 1148 counting only the distinct ones).

The product of its (nonzero) digits is 2612736, while the sum is 53.

The square root of 664979840 is about 25787.2030278586. The cubic root of 664979840 is about 872.8430530316.

The spelling of 664979840 in words is "six hundred sixty-four million, nine hundred seventy-nine thousand, eight hundred forty".