1665649440 has 768 divisors, whose sum is σ = 7586611200. Its totient is φ = 331444224.

The previous prime is 1665649429. The next prime is 1665649457. The reversal of 1665649440 is 449465661.

It is a happy number.

1665649440 is a `hidden beast` number, since 166 + 5 + 6 + 49 + 440 = 666.

It is a Harshad number since it is a multiple of its sum of digits (45).

It is an unprimeable number.

It is a polite number, since it can be written in 127 ways as a sum of consecutive naturals, for example, 7469169 + ... + 7469391.

It is an arithmetic number, because the mean of its divisors is an integer number (9878400).

Almost surely, 2^1665649440 is an apocalyptic number.

1665649440 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 1665649440, and also a Zumkeller number, because its divisors can be partitioned in two sets with the same sum (3793305600).

1665649440 is an abundant number, since it is smaller than the sum of its proper divisors (5920961760).

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

1665649440 is a wasteful number, since it uses less digits than its factorization.

1665649440 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 286 (or 272 counting only the distinct ones).

The product of its (nonzero) digits is 622080, while the sum is 45.

The square root of 1665649440 is about 40812.3687134182. The cubic root of 1665649440 is about 1185.3898412921.

The spelling of 1665649440 in words is "one billion, six hundred sixty-five million, six hundred forty-nine thousand, four hundred forty".