191231639 has 4 divisors (see below), whose sum is σ = 191303856. Its totient is φ = 191159424.

The previous prime is 191231611. The next prime is 191231641. The reversal of 191231639 is 936132191.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 936132191 = 563 ⋅1662757.

It is a cyclic number.

It is not a de Polignac number, because 191231639 - 2¹⁶ = 191166103 is a prime.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 191231599 and 191231608.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (191231669) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 31979 + ... + 37484.

It is an arithmetic number, because the mean of its divisors is an integer number (47825964).

Almost surely, 2^191231639 is an apocalyptic number.

191231639 is a deficient number, since it is larger than the sum of its proper divisors (72217).

191231639 is an equidigital number, since it uses as much as digits as its factorization.

191231639 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 72216.

The product of its digits is 8748, while the sum is 35.

The square root of 191231639 is about 13828.6528266495. The cubic root of 191231639 is about 576.1292379357.

The spelling of 191231639 in words is "one hundred ninety-one million, two hundred thirty-one thousand, six hundred thirty-nine".