194109781 has 2 divisors, whose sum is σ = 194109782. Its totient is φ = 194109780.

The previous prime is 194109761. The next prime is 194109793. The reversal of 194109781 is 187901491.

194109781 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 186459025 + 7650756 = 13655^2 + 2766^2 .

It is a cyclic number.

It is not a de Polignac number, because 194109781 - 2⁵ = 194109749 is a prime.

It is a super-2 number, since 2×194109781² = 75357214159735922, which contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (194109761) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 97054890 + 97054891.

It is an arithmetic number, because the mean of its divisors is an integer number (97054891).

Almost surely, 2^194109781 is an apocalyptic number.

It is an amenable number.

194109781 is a deficient number, since it is larger than the sum of its proper divisors (1).

194109781 is an equidigital number, since it uses as much as digits as its factorization.

194109781 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 18144, while the sum is 40.

The square root of 194109781 is about 13932.3286280507. The cubic root of 194109781 is about 579.0052121238.

The spelling of 194109781 in words is "one hundred ninety-four million, one hundred nine thousand, seven hundred eighty-one".