1665549640 has 16 divisors (see below), whose sum is σ = 3747486780. Its totient is φ = 666219840.

The previous prime is 1665549637. The next prime is 1665549643. The reversal of 1665549640 is 469455661.

It is an interprime number because it is at equal distance from previous prime (1665549637) and next prime (1665549643).

It can be written as a sum of positive squares in 2 ways, for example, as 1409101444 + 256448196 = 37538^2 + 16014^2 .

It is not an unprimeable number, because it can be changed into a prime (1665549643) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 20819331 + ... + 20819410.

Almost surely, 2^1665549640 is an apocalyptic number.

1665549640 is a gapful number since it is divisible by the number (10) formed by its first and last digit.

It is an amenable number.

1665549640 is an abundant number, since it is smaller than the sum of its proper divisors (2081937140).

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

1665549640 is a wasteful number, since it uses less digits than its factorization.

1665549640 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 41638752 (or 41638748 counting only the distinct ones).

The product of its (nonzero) digits is 777600, while the sum is 46.

The square root of 1665549640 is about 40811.1460265452. The cubic root of 1665549640 is about 1185.3661659884.

The spelling of 1665549640 in words is "one billion, six hundred sixty-five million, five hundred forty-nine thousand, six hundred forty".