1661231565 has 96 divisors (see below), whose sum is σ = 3546731520. Its totient is φ = 734832000.

The previous prime is 1661231527. The next prime is 1661231597. The reversal of 1661231565 is 5651321661.

1661231565 is a `hidden beast` number, since 1 + 6 + 61 + 2 + 31 + 565 = 666.

It is not a de Polignac number, because 1661231565 - 2⁷ = 1661231437 is a prime.

It is a congruent number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 95 ways as a sum of consecutive naturals, for example, 201015 + ... + 209115.

It is an arithmetic number, because the mean of its divisors is an integer number (36945120).

Almost surely, 2^1661231565 is an apocalyptic number.

1661231565 is a gapful number since it is divisible by the number (15) formed by its first and last digit.

It is an amenable number.

1661231565 is an abundant number, since it is smaller than the sum of its proper divisors (1885499955).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

1661231565 is a wasteful number, since it uses less digits than its factorization.

1661231565 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8160 (or 8147 counting only the distinct ones).

The product of its digits is 32400, while the sum is 36.

The square root of 1661231565 is about 40758.2085597490. The cubic root of 1661231565 is about 1184.3408928805.

The spelling of 1661231565 in words is "one billion, six hundred sixty-one million, two hundred thirty-one thousand, five hundred sixty-five".