1371561561 has 12 divisors (see below), whose sum is σ = 2029465620. Its totient is φ = 892072320.

The previous prime is 1371561557. The next prime is 1371561571. The reversal of 1371561561 is 1651651731.

1371561561 is a `hidden beast` number, since 1 + 37 + 1 + 5 + 61 + 561 = 666.

It can be written as a sum of positive squares in 2 ways, for example, as 287505936 + 1084055625 = 16956^2 + 32925^2 .

It is not a de Polignac number, because 1371561561 - 2² = 1371561557 is a prime.

It is a super-2 number, since 2×1371561561² = 3762362231225513442, which contains 22 as substring.

It is not an unprimeable number, because it can be changed into a prime (1371561571) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1858116 + ... + 1858853.

It is an arithmetic number, because the mean of its divisors is an integer number (169122135).

Almost surely, 2^1371561561 is an apocalyptic number.

It is an amenable number.

1371561561 is a deficient number, since it is larger than the sum of its proper divisors (657904059).

1371561561 is a wasteful number, since it uses less digits than its factorization.

1371561561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3717016 (or 3717013 counting only the distinct ones).

The product of its digits is 18900, while the sum is 36.

The square root of 1371561561 is about 37034.5995118079. The cubic root of 1371561561 is about 1111.0623600718.

The spelling of 1371561561 in words is "one billion, three hundred seventy-one million, five hundred sixty-one thousand, five hundred sixty-one".