191978457 has 16 divisors (see below), whose sum is σ = 279678720. Its totient is φ = 116168400.

The previous prime is 191978377. The next prime is 191978471. The reversal of 191978457 is 754879191.

It is a happy number.

It is not a de Polignac number, because 191978457 - 2⁸ = 191978201 is a prime.

It is not an unprimeable number, because it can be changed into a prime (191978957) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 18594 + ... + 27012.

It is an arithmetic number, because the mean of its divisors is an integer number (17479920).

Almost surely, 2^191978457 is an apocalyptic number.

It is an amenable number.

191978457 is a deficient number, since it is larger than the sum of its proper divisors (87700263).

191978457 is a wasteful number, since it uses less digits than its factorization.

191978457 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 9124.

The product of its digits is 635040, while the sum is 51.

The square root of 191978457 is about 13855.6290726910. The cubic root of 191978457 is about 576.8782506614.

The spelling of 191978457 in words is "one hundred ninety-one million, nine hundred seventy-eight thousand, four hundred fifty-seven".