1661566775 has 12 divisors (see below), whose sum is σ = 2247647064. Its totient is φ = 1208412000.

The previous prime is 1661566771. The next prime is 1661566783. The reversal of 1661566775 is 5776651661.

It is not a de Polignac number, because 1661566775 - 2² = 1661566771 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1661566771) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 3020756 + ... + 3021305.

It is an arithmetic number, because the mean of its divisors is an integer number (187303922).

Almost surely, 2^1661566775 is an apocalyptic number.

1661566775 is a deficient number, since it is larger than the sum of its proper divisors (586080289).

1661566775 is a wasteful number, since it uses less digits than its factorization.

1661566775 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6042082 (or 6042077 counting only the distinct ones).

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

The square root of 1661566775 is about 40762.3205301170. The cubic root of 1661566775 is about 1184.4205478825.

The spelling of 1661566775 in words is "one billion, six hundred sixty-one million, five hundred sixty-six thousand, seven hundred seventy-five".