17940685681 has 2 divisors, whose sum is σ = 17940685682. Its totient is φ = 17940685680.

The previous prime is 17940685663. The next prime is 17940685703. The reversal of 17940685681 is 18658604971.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 13489661025 + 4451024656 = 116145^2 + 66716^2 .

It is an emirp because it is prime and its reverse (18658604971) is a distict prime.

It is a cyclic number.

It is not a de Polignac number, because 17940685681 - 2⁵ = 17940685649 is a prime.

It is a super-2 number, since 2×17940685681² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (17940685181) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 8970342840 + 8970342841.

It is an arithmetic number, because the mean of its divisors is an integer number (8970342841).

Almost surely, 2^17940685681 is an apocalyptic number.

It is an amenable number.

17940685681 is a deficient number, since it is larger than the sum of its proper divisors (1).

17940685681 is an equidigital number, since it uses as much as digits as its factorization.

17940685681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2903040, while the sum is 55.

The spelling of 17940685681 in words is "seventeen billion, nine hundred forty million, six hundred eighty-five thousand, six hundred eighty-one".