108991681 has 2 divisors, whose sum is σ = 108991682. Its totient is φ = 108991680.

The previous prime is 108991669. The next prime is 108991697. The reversal of 108991681 is 186199801.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 92467456 + 16524225 = 9616^2 + 4065^2 .

It is an emirp because it is prime and its reverse (186199801) is a distict prime. It is also a bemirp because it and its reverse can be mirrored producing other two distinct primes, 189166801 and 108661981.

It is a cyclic number.

It is not a de Polignac number, because 108991681 - 2¹⁹ = 108467393 is a prime.

It is a super-2 number, since 2×108991681² = 23758373054411522, which contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (108991601) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 54495840 + 54495841.

It is an arithmetic number, because the mean of its divisors is an integer number (54495841).

Almost surely, 2^108991681 is an apocalyptic number.

It is an amenable number.

108991681 is a deficient number, since it is larger than the sum of its proper divisors (1).

108991681 is an equidigital number, since it uses as much as digits as its factorization.

108991681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 31104, while the sum is 43.

The square root of 108991681 is about 10439.9080934652. The cubic root of 108991681 is about 477.6734652969.

The spelling of 108991681 in words is "one hundred eight million, nine hundred ninety-one thousand, six hundred eighty-one".