991997443408 has 40 divisors (see below), whose sum is σ = 1954766895840. Its totient is φ = 487612245120.

The previous prime is 991997443391. The next prime is 991997443433. The reversal of 991997443408 is 804344799199.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 1987323 + ... + 2435866.

It is an arithmetic number, because the mean of its divisors is an integer number (48869172396).

Almost surely, 2^991997443408 is an apocalyptic number.

It is an amenable number.

991997443408 is a deficient number, since it is larger than the sum of its proper divisors (962769452432).

991997443408 is a wasteful number, since it uses less digits than its factorization.

991997443408 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4423435 (or 4423429 counting only the distinct ones).

The product of its (nonzero) digits is 70543872, while the sum is 67.

The spelling of 991997443408 in words is "nine hundred ninety-one billion, nine hundred ninety-seven million, four hundred forty-three thousand, four hundred eight".