1561506665 has 8 divisors (see below), whose sum is σ = 1874525568. Its totient is φ = 1248726960.

The previous prime is 1561506649. The next prime is 1561506707. The reversal of 1561506665 is 5666051651.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 1561506665 - 2⁴ = 1561506649 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 45107 + ... + 71816.

It is an arithmetic number, because the mean of its divisors is an integer number (234315696).

Almost surely, 2^1561506665 is an apocalyptic number.

It is an amenable number.

1561506665 is a deficient number, since it is larger than the sum of its proper divisors (313018903).

1561506665 is a wasteful number, since it uses less digits than its factorization.

1561506665 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 119599.

The product of its (nonzero) digits is 162000, while the sum is 41.

The square root of 1561506665 is about 39515.9039501819. The cubic root of 1561506665 is about 1160.1512548011.

The spelling of 1561506665 in words is "one billion, five hundred sixty-one million, five hundred six thousand, six hundred sixty-five".