1661873665 has 16 divisors (see below), whose sum is σ = 2108246400. Its totient is φ = 1254102912.

The previous prime is 1661873659. The next prime is 1661873677. The reversal of 1661873665 is 5663781661.

It is a happy number.

It is a cyclic number.

It is not a de Polignac number, because 1661873665 - 2⁹ = 1661873153 is a prime.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 15405 + ... + 59674.

It is an arithmetic number, because the mean of its divisors is an integer number (131765400).

Almost surely, 2^1661873665 is an apocalyptic number.

It is an amenable number.

1661873665 is a deficient number, since it is larger than the sum of its proper divisors (446372735).

1661873665 is a wasteful number, since it uses less digits than its factorization.

1661873665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 75336.

The product of its digits is 1088640, while the sum is 49.

The square root of 1661873665 is about 40766.0847396460. The cubic root of 1661873665 is about 1184.4934638899.

The spelling of 1661873665 in words is "one billion, six hundred sixty-one million, eight hundred seventy-three thousand, six hundred sixty-five".