61718877581 has 2 divisors, whose sum is σ = 61718877582. Its totient is φ = 61718877580.

The previous prime is 61718877569. The next prime is 61718877607. The reversal of 61718877581 is 18577881716.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 31981599556 + 29737278025 = 178834^2 + 172445^2 .

It is a cyclic number.

It is not a de Polignac number, because 61718877581 - 2¹⁸ = 61718615437 is a prime.

It is a super-2 number, since 2×61718877581² (a number of 22 digits) contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a self number, because there is not a number n which added to its sum of digits gives 61718877581.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (61718870581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 30859438790 + 30859438791.

It is an arithmetic number, because the mean of its divisors is an integer number (30859438791).

Almost surely, 2^61718877581 is an apocalyptic number.

It is an amenable number.

61718877581 is a deficient number, since it is larger than the sum of its proper divisors (1).

61718877581 is an equidigital number, since it uses as much as digits as its factorization.

61718877581 is an evil number, because the sum of its binary digits is even.

The product of its digits is 5268480, while the sum is 59.

The spelling of 61718877581 in words is "sixty-one billion, seven hundred eighteen million, eight hundred seventy-seven thousand, five hundred eighty-one".