190891991 has 6 divisors (see below), whose sum is σ = 196192080. Its totient is φ = 185731416.

The previous prime is 190891979. The next prime is 190892041. The reversal of 190891991 is 199198091.

190891991 = 1256² + 1257² + ... + 1366².

It is a happy number.

It is a de Polignac number, because none of the positive numbers 2^k-190891991 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (190891091) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 68351 + ... + 71088.

It is an arithmetic number, because the mean of its divisors is an integer number (32698680).

Almost surely, 2^190891991 is an apocalyptic number.

190891991 is a deficient number, since it is larger than the sum of its proper divisors (5300089).

190891991 is an equidigital number, since it uses as much as digits as its factorization.

190891991 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 139513 (or 139476 counting only the distinct ones).

The product of its (nonzero) digits is 52488, while the sum is 47.

The square root of 190891991 is about 13816.3667800185. The cubic root of 190891991 is about 575.7879465937.

The spelling of 190891991 in words is "one hundred ninety million, eight hundred ninety-one thousand, nine hundred ninety-one".