991557127835 has 4 divisors (see below), whose sum is σ = 1189868553408. Its totient is φ = 793245702264.

The previous prime is 991557127823. The next prime is 991557127843. The reversal of 991557127835 is 538721755199.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 538721755199 = 1429 ⋅376992131.

It is a cyclic number.

It is not a de Polignac number, because 991557127835 - 2⁴ = 991557127819 is a prime.

It is a Duffinian number.

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 99155712779 + ... + 99155712788.

It is an arithmetic number, because the mean of its divisors is an integer number (297467138352).

Almost surely, 2^991557127835 is an apocalyptic number.

991557127835 is a deficient number, since it is larger than the sum of its proper divisors (198311425573).

991557127835 is a wasteful number, since it uses less digits than its factorization.

991557127835 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 198311425572.

The product of its digits is 23814000, while the sum is 62.

The spelling of 991557127835 in words is "nine hundred ninety-one billion, five hundred fifty-seven million, one hundred twenty-seven thousand, eight hundred thirty-five".