191389956521 has 2 divisors, whose sum is σ = 191389956522. Its totient is φ = 191389956520.

The previous prime is 191389956469. The next prime is 191389956539. The reversal of 191389956521 is 125659983191.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 189628895296 + 1761061225 = 435464^2 + 41965^2 .

It is an emirp because it is prime and its reverse (125659983191) is a distict prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-191389956521 is a prime.

It is a super-2 number, since 2×191389956521² (a number of 23 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (191389956551) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95694978260 + 95694978261.

It is an arithmetic number, because the mean of its divisors is an integer number (95694978261).

Almost surely, 2^191389956521 is an apocalyptic number.

It is an amenable number.

191389956521 is a deficient number, since it is larger than the sum of its proper divisors (1).

191389956521 is an equidigital number, since it uses as much as digits as its factorization.

191389956521 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 5248800, while the sum is 59.

The spelling of 191389956521 in words is "one hundred ninety-one billion, three hundred eighty-nine million, nine hundred fifty-six thousand, five hundred twenty-one".