1561561 has 4 divisors (see below), whose sum is σ = 1577124. Its totient is φ = 1546000.

The previous prime is 1561559. The next prime is 1561577. The reversal of 1561561 is 1651651.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 1651651 = 19 ⋅86929.

It can be written as a sum of positive squares in 2 ways, for example, as 990025 + 571536 = 995^2 + 756^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561561 - 2¹ = 1561559 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (1561541) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7630 + ... + 7831.

It is an arithmetic number, because the mean of its divisors is an integer number (394281).

2^1561561 is an apocalyptic number.

It is an amenable number.

1561561 is a deficient number, since it is larger than the sum of its proper divisors (15563).

1561561 is a wasteful number, since it uses less digits than its factorization.

1561561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 15562.

The product of its digits is 900, while the sum is 25.

The square root of 1561561 is about 1249.6243435529. The cubic root of 1561561 is about 116.0164711054.

The spelling of 1561561 in words is "one million, five hundred sixty-one thousand, five hundred sixty-one".