191785921 has 2 divisors, whose sum is σ = 191785922. Its totient is φ = 191785920.

The previous prime is 191785907. The next prime is 191785927. The reversal of 191785921 is 129587191.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 143065521 + 48720400 = 11961^2 + 6980^2 .

It is a cyclic number.

It is not a de Polignac number, because 191785921 - 2⁷ = 191785793 is a prime.

It is not a weakly prime, because it can be changed into another prime (191785927) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95892960 + 95892961.

It is an arithmetic number, because the mean of its divisors is an integer number (95892961).

Almost surely, 2^191785921 is an apocalyptic number.

It is an amenable number.

191785921 is a deficient number, since it is larger than the sum of its proper divisors (1).

191785921 is an equidigital number, since it uses as much as digits as its factorization.

191785921 is an evil number, because the sum of its binary digits is even.

The product of its digits is 45360, while the sum is 43.

The square root of 191785921 is about 13848.6793955236. The cubic root of 191785921 is about 576.6853349491.

The spelling of 191785921 in words is "one hundred ninety-one million, seven hundred eighty-five thousand, nine hundred twenty-one".