1005168661561 has 9 divisors (see below), whose sum is σ = 1007247288621. Its totient is φ = 1003094321472.

The previous prime is 1005168661531. The next prime is 1005168661597. The reversal of 1005168661561 is 1651668615001.

It is a happy number.

The square root of 1005168661561 is 1002581.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in 4 ways, for example, as 39469371561 + 965699290000 = 198669^2 + 982700^2 .

It is not a de Polignac number, because 1005168661561 - 2⁵ = 1005168661529 is a prime.

It is a super-3 number, since 3×1005168661561³ (a number of 37 digits) contains 333 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1005168661531) 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 8 ways as a sum of consecutive naturals, for example, 774994465 + ... + 774995761.

Almost surely, 2^{1005168661561} is an apocalyptic number.

1005168661561 is the 1002581-st square number.

1005168661561 is the 501291-st centered octagonal number.

It is an amenable number.

1005168661561 is a deficient number, since it is larger than the sum of its proper divisors (2078627060).

1005168661561 is an frugal number, since it uses more digits than its factorization.

1005168661561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4140 (or 2070 counting only the distinct ones).

The product of its (nonzero) digits is 259200, while the sum is 46.

The spelling of 1005168661561 in words is "one trillion, five billion, one hundred sixty-eight million, six hundred sixty-one thousand, five hundred sixty-one".