665618400 has 216 divisors, whose sum is σ = 2364223680. Its totient is φ = 176209920.

The previous prime is 665618399. The next prime is 665618441. The reversal of 665618400 is 4816566.

665618400 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

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

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 35 ways as a sum of consecutive naturals, for example, 1389361 + ... + 1389839.

It is an arithmetic number, because the mean of its divisors is an integer number (10945480).

Almost surely, 2^665618400 is an apocalyptic number.

665618400 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 665618400, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1182111840).

665618400 is an abundant number, since it is smaller than the sum of its proper divisors (1698605280).

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

665618400 is a wasteful number, since it uses less digits than its factorization.

665618400 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 698 (or 682 counting only the distinct ones).

The product of its (nonzero) digits is 34560, while the sum is 36.

The square root of 665618400 is about 25799.5813919529. The cubic root of 665618400 is about 873.1223518992.

The spelling of 665618400 in words is "six hundred sixty-five million, six hundred eighteen thousand, four hundred".