1665775661 has 6 divisors (see below), whose sum is σ = 1830976686. Its totient is φ = 1514341400.

The previous prime is 1665775591. The next prime is 1665775663.

1665775661 is nontrivially palindromic in base 10.

It can be written as a sum of positive squares in only one way, i.e., 1524902500 + 140873161 = 39050^2 + 11869^2 .

It is not a de Polignac number, because 1665775661 - 2¹⁰ = 1665774637 is a prime.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1665775663) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 6883250 + ... + 6883491.

It is an arithmetic number, because the mean of its divisors is an integer number (305162781).

Almost surely, 2^1665775661 is an apocalyptic number.

1665775661 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1665775661 is a deficient number, since it is larger than the sum of its proper divisors (165201025).

1665775661 is a wasteful number, since it uses less digits than its factorization.

1665775661 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 13766763 (or 13766752 counting only the distinct ones).

The product of its digits is 1587600, while the sum is 50.

The square root of 1665775661 is about 40813.9150413189. The cubic root of 1665775661 is about 1185.4197830290.

The spelling of 1665775661 in words is "one billion, six hundred sixty-five million, seven hundred seventy-five thousand, six hundred sixty-one".