1665256320 has 640 divisors, whose sum is σ = 7340034240. Its totient is φ = 350355456.

The previous prime is 1665256309. The next prime is 1665256321. The reversal of 1665256320 is 236525661.

It is a happy number.

1665256320 is a `hidden beast` number, since 16 + 6 + 5 + 2 + 5 + 632 + 0 = 666.

It is a tau number, because it is divible by the number of its divisors (640).

It is a super-2 number, since 2×1665256320² = 5546157222599884800, which contains 22 as substring.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1665256321) by changing a digit.

It is a polite number, since it can be written in 79 ways as a sum of consecutive naturals, for example, 4717264 + ... + 4717616.

Almost surely, 2^1665256320 is an apocalyptic number.

1665256320 is a gapful number since it is divisible by the number (10) 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 1665256320, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3670017120).

1665256320 is an abundant number, since it is smaller than the sum of its proper divisors (5674777920).

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

1665256320 is a wasteful number, since it uses less digits than its factorization.

1665256320 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 404 (or 383 counting only the distinct ones).

The product of its (nonzero) digits is 64800, while the sum is 36.

The square root of 1665256320 is about 40807.5522422014. The cubic root of 1665256320 is about 1185.2965769454.

The spelling of 1665256320 in words is "one billion, six hundred sixty-five million, two hundred fifty-six thousand, three hundred twenty".