1561445221 has 6 divisors (see below), whose sum is σ = 1816375110. Its totient is φ = 1338381576.

The previous prime is 1561445209. The next prime is 1561445261. The reversal of 1561445221 is 1225441651.

It is a happy number.

It can be written as a sum of positive squares in only one way, i.e., 906852996 + 654592225 = 30114^2 + 25585^2 .

It is not a de Polignac number, because 1561445221 - 2¹⁷ = 1561314149 is a prime.

It is a super-2 number, since 2×1561445221² = 4876222356367477682, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (1561445261) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 15933066 + ... + 15933163.

It is an arithmetic number, because the mean of its divisors is an integer number (302729185).

Almost surely, 2^1561445221 is an apocalyptic number.

It is an amenable number.

1561445221 is a deficient number, since it is larger than the sum of its proper divisors (254929889).

1561445221 is an equidigital number, since it uses as much as digits as its factorization.

1561445221 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 31866243 (or 31866236 counting only the distinct ones).

The product of its digits is 9600, while the sum is 31.

The square root of 1561445221 is about 39515.1264834114. The cubic root of 1561445221 is about 1160.1360376030.

Adding to 1561445221 its reverse (1225441651), we get a palindrome (2786886872).

The spelling of 1561445221 in words is "one billion, five hundred sixty-one million, four hundred forty-five thousand, two hundred twenty-one".