5661991665 has 64 divisors (see below), whose sum is σ = 11014963200. Its totient is φ = 2736676800.

The previous prime is 5661991663. The next prime is 5661991669.

5661991665 is a `hidden beast` number, since 5 + 6 + 619 + 9 + 16 + 6 + 5 = 666.

5661991665 is nontrivially palindromic in base 10.

5661991665 is digitally balanced in base 3, because in such base it contains all the possibile digits an equal number of times.

It is not a de Polignac number, because 5661991665 - 2¹ = 5661991663 is a prime.

It is a super-2 number, since 2×5661991665² = 64116299229058944450, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (5661991663) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 63 ways as a sum of consecutive naturals, for example, 485776 + ... + 497294.

It is an arithmetic number, because the mean of its divisors is an integer number (172108800).

Almost surely, 2^5661991665 is an apocalyptic number.

5661991665 is a gapful number since it is divisible by the number (55) formed by its first and last digit.

It is an amenable number.

5661991665 is a deficient number, since it is larger than the sum of its proper divisors (5352971535).

5661991665 is a wasteful number, since it uses less digits than its factorization.

5661991665 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 11875 (or 11869 counting only the distinct ones).

The product of its digits is 2624400, while the sum is 54.

The square root of 5661991665 is about 75246.2069808173. The cubic root of 5661991665 is about 1782.3366679030.

The spelling of 5661991665 in words is "five billion, six hundred sixty-one million, nine hundred ninety-one thousand, six hundred sixty-five".