991356712521 has 16 divisors (see below), whose sum is σ = 1559369084928. Its totient is φ = 548215693200.

The previous prime is 991356712477. The next prime is 991356712561. The reversal of 991356712521 is 125217653199.

It is not a de Polignac number, because 991356712521 - 2¹¹ = 991356710473 is a prime.

It is a super-3 number, since 3×991356712521³ (a number of 37 digits) contains 333 as substring.

It is not an unprimeable number, because it can be changed into a prime (991356712561) by changing a digit.

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 15 ways as a sum of consecutive naturals, for example, 761410035 + ... + 761411336.

It is an arithmetic number, because the mean of its divisors is an integer number (97460567808).

Almost surely, 2^991356712521 is an apocalyptic number.

It is an amenable number.

991356712521 is a deficient number, since it is larger than the sum of its proper divisors (568012372407).

991356712521 is a wasteful number, since it uses less digits than its factorization.

991356712521 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1522821412.

The product of its digits is 1020600, while the sum is 51.

The spelling of 991356712521 in words is "nine hundred ninety-one billion, three hundred fifty-six million, seven hundred twelve thousand, five hundred twenty-one".