1611378665 has 24 divisors (see below), whose sum is σ = 2100202440. Its totient is φ = 1186834272.

The previous prime is 1611378661. The next prime is 1611378673. The reversal of 1611378665 is 5668731161.

It can be written as a sum of positive squares in 4 ways, for example, as 600838144 + 1010540521 = 24512^2 + 31789^2 .

It is not a de Polignac number, because 1611378665 - 2² = 1611378661 is a prime.

Its product of digits (181440) is a multiple of the sum of its prime factors (810).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1611378661) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 4207064 + ... + 4207446.

It is an arithmetic number, because the mean of its divisors is an integer number (87508435).

Almost surely, 2^1611378665 is an apocalyptic number.

It is an amenable number.

1611378665 is a deficient number, since it is larger than the sum of its proper divisors (488823775).

1611378665 is an frugal number, since it uses more digits than its factorization.

1611378665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 810 (or 401 counting only the distinct ones).

The product of its digits is 181440, while the sum is 44.

The square root of 1611378665 is about 40141.9813287785. The cubic root of 1611378665 is about 1172.3731666776.

The spelling of 1611378665 in words is "one billion, six hundred eleven million, three hundred seventy-eight thousand, six hundred sixty-five".