191921861009 has 2 divisors, whose sum is σ = 191921861010. Its totient is φ = 191921861008.

The previous prime is 191921860943. The next prime is 191921861059. The reversal of 191921861009 is 900168129191.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 183136923025 + 8784937984 = 427945^2 + 93728^2 .

It is a cyclic number.

It is not a de Polignac number, because 191921861009 - 2¹⁶ = 191921795473 is a prime.

It is not a weakly prime, because it can be changed into another prime (191921861059) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95960930504 + 95960930505.

It is an arithmetic number, because the mean of its divisors is an integer number (95960930505).

Almost surely, 2^191921861009 is an apocalyptic number.

It is an amenable number.

191921861009 is a deficient number, since it is larger than the sum of its proper divisors (1).

191921861009 is an equidigital number, since it uses as much as digits as its factorization.

191921861009 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 69984, while the sum is 47.

The spelling of 191921861009 in words is "one hundred ninety-one billion, nine hundred twenty-one million, eight hundred sixty-one thousand, nine".