191920681 has 2 divisors, whose sum is σ = 191920682. Its totient is φ = 191920680.

The previous prime is 191920679. The next prime is 191920709. The reversal of 191920681 is 186029191.

191920681 is digitally balanced in base 2, because in such base it contains all the possibile digits an equal number of times.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 150896656 + 41024025 = 12284^2 + 6405^2 .

It is a cyclic number.

It is not a de Polignac number, because 191920681 - 2¹ = 191920679 is a prime.

It is a super-2 number, since 2×191920681² = 73667095591007522, which contains 22 as substring.

Together with 191920679, it forms a pair of twin primes.

It is a Chen prime.

It is a zygodrome in base 9.

It is a self number, because there is not a number n which added to its sum of digits gives 191920681.

It is not a weakly prime, because it can be changed into another prime (191920381) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95960340 + 95960341.

It is an arithmetic number, because the mean of its divisors is an integer number (95960341).

Almost surely, 2^191920681 is an apocalyptic number.

It is an amenable number.

191920681 is a deficient number, since it is larger than the sum of its proper divisors (1).

191920681 is an equidigital number, since it uses as much as digits as its factorization.

191920681 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 7776, while the sum is 37.

The square root of 191920681 is about 13853.5439870092. The cubic root of 191920681 is about 576.8203742684.

The spelling of 191920681 in words is "one hundred ninety-one million, nine hundred twenty thousand, six hundred eighty-one".