191390667421 has 2 divisors, whose sum is σ = 191390667422. Its totient is φ = 191390667420.

The previous prime is 191390667359. The next prime is 191390667439. The reversal of 191390667421 is 124766093191.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 147882548025 + 43508119396 = 384555^2 + 208586^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-191390667421 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (191390667451) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95695333710 + 95695333711.

It is an arithmetic number, because the mean of its divisors is an integer number (95695333711).

Almost surely, 2^191390667421 is an apocalyptic number.

It is an amenable number.

191390667421 is a deficient number, since it is larger than the sum of its proper divisors (1).

191390667421 is an equidigital number, since it uses as much as digits as its factorization.

191390667421 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 489888, while the sum is 49.

The spelling of 191390667421 in words is "one hundred ninety-one billion, three hundred ninety million, six hundred sixty-seven thousand, four hundred twenty-one".