991209208549 has 32 divisors (see below), whose sum is σ = 1199464611840. Its totient is φ = 801007704000.

The previous prime is 991209208537. The next prime is 991209208559. The reversal of 991209208549 is 945802902199.

It is not a de Polignac number, because 991209208549 - 2¹¹ = 991209206501 is a prime.

It is a super-2 number, since 2×991209208549² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 991209208493 and 991209208502.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991209208559) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 35347164 + ... + 35375194.

It is an arithmetic number, because the mean of its divisors is an integer number (37483269120).

Almost surely, 2^991209208549 is an apocalyptic number.

It is an amenable number.

991209208549 is a deficient number, since it is larger than the sum of its proper divisors (208255403291).

991209208549 is a wasteful number, since it uses less digits than its factorization.

991209208549 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 32161.

The product of its (nonzero) digits is 4199040, while the sum is 58.

The spelling of 991209208549 in words is "nine hundred ninety-one billion, two hundred nine million, two hundred eight thousand, five hundred forty-nine".