991746204181 has 4 divisors (see below), whose sum is σ = 991748504032. Its totient is φ = 991743904332.

The previous prime is 991746204139. The next prime is 991746204199. The reversal of 991746204181 is 181402647199.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a 3-Lehmer number, since φ(991746204181) divides (991746204181-1)³.

It is a cyclic number.

It is not a de Polignac number, because 991746204181 - 2²³ = 991737815573 is a prime.

It is a super-2 number, since 2×991746204181² (a number of 25 digits) contains 22 as substring.

It is a deceptive number, since it divides R_991746204180.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991746294181) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 287481 + ... + 1437406.

It is an arithmetic number, because the mean of its divisors is an integer number (247937126008).

It is a Poulet number, since it divides 2^991746204180-1.

Almost surely, 2^991746204181 is an apocalyptic number.

991746204181 is the 574963-rd octagonal number.

It is an amenable number.

991746204181 is a deficient number, since it is larger than the sum of its proper divisors (2299851).

991746204181 is a wasteful number, since it uses less digits than its factorization.

991746204181 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2299850.

The product of its (nonzero) digits is 870912, while the sum is 52.

The spelling of 991746204181 in words is "nine hundred ninety-one billion, seven hundred forty-six million, two hundred four thousand, one hundred eighty-one".