1561271761 has 6 divisors (see below), whose sum is σ = 1816173330. Its totient is φ = 1338232896.

The previous prime is 1561271741. The next prime is 1561271773. The reversal of 1561271761 is 1671721651.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 1186113600 + 375158161 = 34440^2 + 19369^2 .

It is not a de Polignac number, because 1561271761 - 2¹¹ = 1561269713 is a prime.

It is a super-2 number, since 2×1561271761² = 4875139023392082242, which contains 22 as substring.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 1561271761.

It is not an unprimeable number, because it can be changed into a prime (1561271741) 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 5 ways as a sum of consecutive naturals, for example, 15931296 + ... + 15931393.

It is an arithmetic number, because the mean of its divisors is an integer number (302695555).

Almost surely, 2^1561271761 is an apocalyptic number.

It is an amenable number.

1561271761 is a deficient number, since it is larger than the sum of its proper divisors (254901569).

1561271761 is an equidigital number, since it uses as much as digits as its factorization.

1561271761 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31862703 (or 31862696 counting only the distinct ones).

The product of its digits is 17640, while the sum is 37.

The square root of 1561271761 is about 39512.9315667668. The cubic root of 1561271761 is about 1160.0930764098.

The spelling of 1561271761 in words is "one billion, five hundred sixty-one million, two hundred seventy-one thousand, seven hundred sixty-one".