1561565281 has 2 divisors, whose sum is σ = 1561565282. Its totient is φ = 1561565280.

The previous prime is 1561565249. The next prime is 1561565287. The reversal of 1561565281 is 1825651651.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1033301025 + 528264256 = 32145^2 + 22984^2 .

It is a cyclic number.

It is not a de Polignac number, because 1561565281 - 2⁵ = 1561565249 is a prime.

It is a super-2 number, since 2×1561565281² = 4876972253649217922, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (1561565287) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 780782640 + 780782641.

It is an arithmetic number, because the mean of its divisors is an integer number (780782641).

Almost surely, 2^1561565281 is an apocalyptic number.

It is an amenable number.

1561565281 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561565281 is an equidigital number, since it uses as much as digits as its factorization.

1561565281 is an evil number, because the sum of its binary digits is even.

The product of its digits is 72000, while the sum is 40.

The square root of 1561565281 is about 39516.6456192830. The cubic root of 1561565281 is about 1160.1657712457.

The spelling of 1561565281 in words is "one billion, five hundred sixty-one million, five hundred sixty-five thousand, two hundred eighty-one".