191565421 has 2 divisors, whose sum is σ = 191565422. Its totient is φ = 191565420.

The previous prime is 191565383. The next prime is 191565427. The reversal of 191565421 is 124565191.

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., 188375625 + 3189796 = 13725^2 + 1786^2 .

It is a cyclic number.

It is not a de Polignac number, because 191565421 - 2⁹ = 191564909 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (191565427) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95782710 + 95782711.

It is an arithmetic number, because the mean of its divisors is an integer number (95782711).

Almost surely, 2^191565421 is an apocalyptic number.

It is an amenable number.

191565421 is a deficient number, since it is larger than the sum of its proper divisors (1).

191565421 is an equidigital number, since it uses as much as digits as its factorization.

191565421 is an evil number, because the sum of its binary digits is even.

The product of its digits is 10800, while the sum is 34.

The square root of 191565421 is about 13840.7160580658. The cubic root of 191565421 is about 576.4642414171.

The spelling of 191565421 in words is "one hundred ninety-one million, five hundred sixty-five thousand, four hundred twenty-one".