191521 has 8 divisors (see below), whose sum is σ = 218304. Its totient is φ = 166320.

The previous prime is 191519. The next prime is 191531. The reversal of 191521 is 125191.

191521 is nontrivially palindromic in base 7.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 191521 - 2¹ = 191519 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (191531) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 126 + ... + 631.

It is an arithmetic number, because the mean of its divisors is an integer number (27288).

2¹⁹¹⁵²¹ is an apocalyptic number.

191521 is a gapful number since it is divisible by the number (11) formed by its first and last digit.

191521 is the 253-rd octagonal number.

It is an amenable number.

191521 is a deficient number, since it is larger than the sum of its proper divisors (26783).

191521 is a wasteful number, since it uses less digits than its factorization.

191521 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 791.

The product of its digits is 90, while the sum is 19.

The square root of 191521 is about 437.6311232077. The cubic root of 191521 is about 57.6419680317.

It can be divided in two parts, 1915 and 21, that added together give a square (1936 = 44²).

The spelling of 191521 in words is "one hundred ninety-one thousand, five hundred twenty-one".