665761320 has 288 divisors, whose sum is σ = 2549439360. Its totient is φ = 147571200.

The previous prime is 665761319. The next prime is 665761331. The reversal of 665761320 is 23167566.

665761320 is a `hidden beast` number, since 66 + 576 + 1 + 3 + 20 = 666.

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

It is an unprimeable number.

It is a polite number, since it can be written in 71 ways as a sum of consecutive naturals, for example, 9376885 + ... + 9376955.

It is an arithmetic number, because the mean of its divisors is an integer number (8852220).

Almost surely, 2^665761320 is an apocalyptic number.

665761320 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 665761320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (1274719680).

665761320 is an abundant number, since it is smaller than the sum of its proper divisors (1883678040).

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

665761320 is a wasteful number, since it uses less digits than its factorization.

665761320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 217 (or 149 counting only the distinct ones).

The product of its (nonzero) digits is 45360, while the sum is 36.

The square root of 665761320 is about 25802.3510556693. The cubic root of 665761320 is about 873.1848390121.

It can be divided in two parts, 66576 and 1320, that added together give a triangular number (67896 = T₃₆₈).

The spelling of 665761320 in words is "six hundred sixty-five million, seven hundred sixty-one thousand, three hundred twenty".