27561561637 has 2 divisors, whose sum is σ = 27561561638. Its totient is φ = 27561561636.

The previous prime is 27561561451. The next prime is 27561561683. The reversal of 27561561637 is 73616516572.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 15531639876 + 12029921761 = 124626^2 + 109681^2 .

It is a cyclic number.

It is not a de Polignac number, because 27561561637 - 2¹⁹ = 27561037349 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (27561561697) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 13780780818 + 13780780819.

It is an arithmetic number, because the mean of its divisors is an integer number (13780780819).

Almost surely, 2^27561561637 is an apocalyptic number.

It is an amenable number.

27561561637 is a deficient number, since it is larger than the sum of its proper divisors (1).

27561561637 is an equidigital number, since it uses as much as digits as its factorization.

27561561637 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1587600, while the sum is 49.

The spelling of 27561561637 in words is "twenty-seven billion, five hundred sixty-one million, five hundred sixty-one thousand, six hundred thirty-seven".