191990087539 has 4 divisors (see below), whose sum is σ = 191991094056. Its totient is φ = 191989081024.

The previous prime is 191990087533. The next prime is 191990087543. The reversal of 191990087539 is 935780099191.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 191990087539 - 2³⁷ = 54551134067 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (191990087533) 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, 119689 + ... + 631114.

It is an arithmetic number, because the mean of its divisors is an integer number (47997773514).

Almost surely, 2^191990087539 is an apocalyptic number.

191990087539 is a deficient number, since it is larger than the sum of its proper divisors (1006517).

191990087539 is an equidigital number, since it uses as much as digits as its factorization.

191990087539 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 1006516.

The product of its (nonzero) digits is 5511240, while the sum is 61.

The spelling of 191990087539 in words is "one hundred ninety-one billion, nine hundred ninety million, eighty-seven thousand, five hundred thirty-nine".