191531 has 2 divisors, whose sum is σ = 191532. Its totient is φ = 191530.

The previous prime is 191519. The next prime is 191533. The reversal of 191531 is 135191.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 191531 - 2⁶ = 191467 is a prime.

It is a super-2 number, since 2×191531² = 73368247922, which contains 22 as substring.

Together with 191533, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (191533) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 95765 + 95766.

It is an arithmetic number, because the mean of its divisors is an integer number (95766).

2¹⁹¹⁵³¹ is an apocalyptic number.

191531 is a deficient number, since it is larger than the sum of its proper divisors (1).

191531 is an equidigital number, since it uses as much as digits as its factorization.

191531 is an evil number, because the sum of its binary digits is even.

The product of its digits is 135, while the sum is 20.

The square root of 191531 is about 437.6425482057. The cubic root of 191531 is about 57.6429712457.

The spelling of 191531 in words is "one hundred ninety-one thousand, five hundred thirty-one".