684545881561 has 4 divisors (see below), whose sum is σ = 684548437300. Its totient is φ = 684543325824.

The previous prime is 684545881471. The next prime is 684545881619. The reversal of 684545881561 is 165188545486.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 165188545486 = 2 ⋅82594272743.

It can be written as a sum of positive squares in 2 ways, for example, as 85711345225 + 598834536336 = 292765^2 + 773844^2 .

It is a cyclic number.

It is not a de Polignac number, because 684545881561 - 2¹⁹ = 684545357273 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 684545881561.

It is not an unprimeable number, because it can be changed into a prime (684545887561) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 821856 + ... + 1429873.

It is an arithmetic number, because the mean of its divisors is an integer number (171137109325).

Almost surely, 2^684545881561 is an apocalyptic number.

It is an amenable number.

684545881561 is a deficient number, since it is larger than the sum of its proper divisors (2555739).

684545881561 is a wasteful number, since it uses less digits than its factorization.

684545881561 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2555738.

The product of its digits is 36864000, while the sum is 61.

The spelling of 684545881561 in words is "six hundred eighty-four billion, five hundred forty-five million, eight hundred eighty-one thousand, five hundred sixty-one".