61555605809 has 2 divisors, whose sum is σ = 61555605810. Its totient is φ = 61555605808.

The previous prime is 61555605803. The next prime is 61555605817. The reversal of 61555605809 is 90850655516.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 48167958784 + 13387647025 = 219472^2 + 115705^2 .

It is a cyclic number.

It is not a de Polignac number, because 61555605809 - 2¹² = 61555601713 is a prime.

It is not a weakly prime, because it can be changed into another prime (61555605803) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30777802904 + 30777802905.

It is an arithmetic number, because the mean of its divisors is an integer number (30777802905).

Almost surely, 2^61555605809 is an apocalyptic number.

It is an amenable number.

61555605809 is a deficient number, since it is larger than the sum of its proper divisors (1).

61555605809 is an equidigital number, since it uses as much as digits as its factorization.

61555605809 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1620000, while the sum is 50.

The spelling of 61555605809 in words is "sixty-one billion, five hundred fifty-five million, six hundred five thousand, eight hundred nine".