1156661561 has 4 divisors (see below), whose sum is σ = 1261812624. Its totient is φ = 1051510500.

The previous prime is 1156661557. The next prime is 1156661563. The reversal of 1156661561 is 1651666511.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is not a de Polignac number, because 1156661561 - 2² = 1156661557 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1156661563) by changing a digit.

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 3 ways as a sum of consecutive naturals, for example, 52575515 + ... + 52575536.

It is an arithmetic number, because the mean of its divisors is an integer number (315453156).

Almost surely, 2^1156661561 is an apocalyptic number.

1156661561 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

It is an amenable number.

1156661561 is a deficient number, since it is larger than the sum of its proper divisors (105151063).

1156661561 is a wasteful number, since it uses less digits than its factorization.

1156661561 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 105151062.

The product of its digits is 32400, while the sum is 38.

The square root of 1156661561 is about 34009.7274467174. The cubic root of 1156661561 is about 1049.7086299624.

The spelling of 1156661561 in words is "one billion, one hundred fifty-six million, six hundred sixty-one thousand, five hundred sixty-one".