1661556505 has 8 divisors (see below), whose sum is σ = 2278706112. Its totient is φ = 1139353008.

The previous prime is 1661556503. The next prime is 1661556539. The reversal of 1661556505 is 5056551661.

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

It is a cyclic number.

It is not a de Polignac number, because 1661556505 - 2¹ = 1661556503 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1661556503) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 23736487 + ... + 23736556.

It is an arithmetic number, because the mean of its divisors is an integer number (284838264).

Almost surely, 2^1661556505 is an apocalyptic number.

It is an amenable number.

1661556505 is a deficient number, since it is larger than the sum of its proper divisors (617149607).

1661556505 is an equidigital number, since it uses as much as digits as its factorization.

1661556505 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 47473055.

The product of its (nonzero) digits is 135000, while the sum is 40.

The square root of 1661556505 is about 40762.1945557400. The cubic root of 1661556505 is about 1184.4181076106.

The spelling of 1661556505 in words is "one billion, six hundred sixty-one million, five hundred fifty-six thousand, five hundred five".