991908393599 has 4 divisors (see below), whose sum is σ = 992127895440. Its totient is φ = 991688891760.

The previous prime is 991908393569. The next prime is 991908393611. The reversal of 991908393599 is 995393809199.

It is a semiprime because it is the product of two primes, and also an emirpimes, since its reverse is a distinct semiprime: 995393809199 = 139 ⋅7161106541.

It is a cyclic number.

It is not a de Polignac number, because 991908393599 - 2²⁴ = 991891616383 is a prime.

It is a super-2 number, since 2×991908393599² (a number of 25 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (991908393559) 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, 109744142 + ... + 109753179.

It is an arithmetic number, because the mean of its divisors is an integer number (248031973860).

Almost surely, 2^991908393599 is an apocalyptic number.

991908393599 is a deficient number, since it is larger than the sum of its proper divisors (219501841).

991908393599 is a wasteful number, since it uses less digits than its factorization.

991908393599 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 219501840.

The product of its (nonzero) digits is 191318760, while the sum is 74.

The spelling of 991908393599 in words is "nine hundred ninety-one billion, nine hundred eight million, three hundred ninety-three thousand, five hundred ninety-nine".