1561264261 has 2 divisors, whose sum is σ = 1561264262. Its totient is φ = 1561264260.

The previous prime is 1561264259. The next prime is 1561264267. The reversal of 1561264261 is 1624621651.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 1560724036 + 540225 = 39506^2 + 735^2 .

It is an emirp because it is prime and its reverse (1624621651) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 1561264261 - 2¹ = 1561264259 is a prime.

It is a super-2 number, since 2×1561264261² = 4875092185351752242, which contains 22 as substring.

Together with 1561264259, it forms a pair of twin primes.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (1561264267) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 780632130 + 780632131.

It is an arithmetic number, because the mean of its divisors is an integer number (780632131).

Almost surely, 2^1561264261 is an apocalyptic number.

It is an amenable number.

1561264261 is a deficient number, since it is larger than the sum of its proper divisors (1).

1561264261 is an equidigital number, since it uses as much as digits as its factorization.

1561264261 is an evil number, because the sum of its binary digits is even.

The product of its digits is 17280, while the sum is 34.

The square root of 1561264261 is about 39512.8366610144. The cubic root of 1561264261 is about 1160.0912187977.

The spelling of 1561264261 in words is "one billion, five hundred sixty-one million, two hundred sixty-four thousand, two hundred sixty-one".