1561112221 has 4 divisors (see below), whose sum is σ = 1561588444. Its totient is φ = 1560636000.

The previous prime is 1561112209. The next prime is 1561112239. The reversal of 1561112221 is 1222111651.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 538008025 + 1023104196 = 23195^2 + 31986^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561112221 - 2¹⁵ = 1561079453 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 1561112192 and 1561112201.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561112921) 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 3 ways as a sum of consecutive naturals, for example, 233160 + ... + 239761.

It is an arithmetic number, because the mean of its divisors is an integer number (390397111).

Almost surely, 2^1561112221 is an apocalyptic number.

It is an amenable number.

1561112221 is a deficient number, since it is larger than the sum of its proper divisors (476223).

1561112221 is an equidigital number, since it uses as much as digits as its factorization.

1561112221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 476222.

The product of its digits is 240, while the sum is 22.

The square root of 1561112221 is about 39510.9126824476. The cubic root of 1561112221 is about 1160.0535600022.

Adding to 1561112221 its reverse (1222111651), we get a palindrome (2783223872).

The spelling of 1561112221 in words is "one billion, five hundred sixty-one million, one hundred twelve thousand, two hundred twenty-one".