1561222081 has 8 divisors (see below), whose sum is σ = 1670102280. Its totient is φ = 1454235648.

The previous prime is 1561222043. The next prime is 1561222087. The reversal of 1561222081 is 1802221651.

It can be written as a sum of positive squares in 4 ways, for example, as 337971456 + 1223250625 = 18384^2 + 34975^2 .

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 1561222081 - 2¹¹ = 1561220033 is a prime.

It is a super-2 number, since 2×1561222081² = 4874828772403941122, which contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1561222087) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 471736 + ... + 475033.

It is an arithmetic number, because the mean of its divisors is an integer number (208762785).

Almost surely, 2^1561222081 is an apocalyptic number.

It is an amenable number.

1561222081 is a deficient number, since it is larger than the sum of its proper divisors (108880199).

1561222081 is an equidigital number, since it uses as much as digits as its factorization.

1561222081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 946883.

The product of its (nonzero) digits is 1920, while the sum is 28.

The square root of 1561222081 is about 39512.3029068163. The cubic root of 1561222081 is about 1160.0807714764.

It can be divided in two parts, 156122 and 2081, that added together give a triangular number (158203 = T₅₆₂).

The spelling of 1561222081 in words is "one billion, five hundred sixty-one million, two hundred twenty-two thousand, eighty-one".