1001561561 has 32 divisors (see below), whose sum is σ = 1353531648. Its totient is φ = 715703040.

The previous prime is 1001561557. The next prime is 1001561591. The reversal of 1001561561 is 1651651001.

It is not a de Polignac number, because 1001561561 - 2² = 1001561557 is a prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 1001561561.

It is not an unprimeable number, because it can be changed into a prime (1001561591) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 153971 + ... + 160343.

It is an arithmetic number, because the mean of its divisors is an integer number (42297864).

Almost surely, 2^1001561561 is an apocalyptic number.

1001561561 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1001561561 is a deficient number, since it is larger than the sum of its proper divisors (351970087).

1001561561 is a wasteful number, since it uses less digits than its factorization.

1001561561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6561.

The product of its (nonzero) digits is 900, while the sum is 26.

The square root of 1001561561 is about 31647.4574176189. The cubic root of 1001561561 is about 1000.5202496267.

The spelling of 1001561561 in words is "one billion, one million, five hundred sixty-one thousand, five hundred sixty-one".