665121600 has 1008 divisors, whose sum is σ = 3095426880. Its totient is φ = 132710400.

The previous prime is 665121593. The next prime is 665121601. The reversal of 665121600 is 6121566.

It is a happy number.

665121600 is a `hidden beast` number, since 6 + 6 + 51 + 2 + 1 + 600 = 666.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (665121601) by changing a digit.

It is a polite number, since it can be written in 143 ways as a sum of consecutive naturals, for example, 35006391 + ... + 35006409.

It is an arithmetic number, because the mean of its divisors is an integer number (3070860).

Almost surely, 2^665121600 is an apocalyptic number.

665121600 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 665121600, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1547713440).

665121600 is an abundant number, since it is smaller than the sum of its proper divisors (2430305280).

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

665121600 is a wasteful number, since it uses less digits than its factorization.

665121600 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 88 (or 70 counting only the distinct ones).

The product of its (nonzero) digits is 2160, while the sum is 27.

The square root of 665121600 is about 25789.9515315559. The cubic root of 665121600 is about 872.9050726760.

It can be divided in two parts, 665 and 121600, that added together give a triangular number (122265 = T₄₉₄).

The spelling of 665121600 in words is "six hundred sixty-five million, one hundred twenty-one thousand, six hundred".