685537537561 has 2 divisors, whose sum is σ = 685537537562. Its totient is φ = 685537537560.

The previous prime is 685537537547. The next prime is 685537537577. The reversal of 685537537561 is 165735735586.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 615063747600 + 70473789961 = 784260^2 + 265469^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-685537537561 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 685537537561.

It is not a weakly prime, because it can be changed into another prime (685537537261) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 342768768780 + 342768768781.

It is an arithmetic number, because the mean of its divisors is an integer number (342768768781).

Almost surely, 2^685537537561 is an apocalyptic number.

It is an amenable number.

685537537561 is a deficient number, since it is larger than the sum of its proper divisors (1).

685537537561 is an equidigital number, since it uses as much as digits as its factorization.

685537537561 is an evil number, because the sum of its binary digits is even.

The product of its digits is 79380000, while the sum is 61.

The spelling of 685537537561 in words is "six hundred eighty-five billion, five hundred thirty-seven million, five hundred thirty-seven thousand, five hundred sixty-one".