1561445261 has 2 divisors, whose sum is σ = 1561445262. Its totient is φ = 1561445260.

The previous prime is 1561445209. The next prime is 1561445269. The reversal of 1561445261 is 1625441651.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 1232712100 + 328733161 = 35110^2 + 18131^2 .

It is an emirp because it is prime and its reverse (1625441651) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1561445261 - 2²² = 1557250957 is a prime.

It is a super-2 number, since 2×1561445261² = 4876222606198716242, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1561445269) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 780722630 + 780722631.

It is an arithmetic number, because the mean of its divisors is an integer number (780722631).

Almost surely, 2^1561445261 is an apocalyptic number.

It is an amenable number.

1561445261 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561445261 is an equidigital number, since it uses as much as digits as its factorization.

1561445261 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 28800, while the sum is 35.

The square root of 1561445261 is about 39515.1269895467. The cubic root of 1561445261 is about 1160.1360475095.

The spelling of 1561445261 in words is "one billion, five hundred sixty-one million, four hundred forty-five thousand, two hundred sixty-one".