991649505856 has 21 divisors (see below), whose sum is σ = 1967820296889. Its totient is φ = 495820769664.

The previous prime is 991649505851. The next prime is 991649505919. The reversal of 991649505856 is 658505946199.

The square root of 991649505856 is 995816.

It is a perfect power (a square), and thus also a powerful number.

It can be written as a sum of positive squares in only one way, i.e., 845737729600 + 145911776256 = 919640^2 + 381984^2 .

It is a Duffinian number.

It is a junction number, because it is equal to n+sod(n) for n = 991649505791 and 991649505800.

It is not an unprimeable number, because it can be changed into a prime (991649505851) by changing a digit.

It is a polite number, since it can be written in 2 ways as a sum of consecutive naturals, for example, 7904290 + ... + 8028766.

Almost surely, 2^991649505856 is an apocalyptic number.

991649505856 is the 995816-th square number.

It is an amenable number.

991649505856 is a deficient number, since it is larger than the sum of its proper divisors (976170791033).

991649505856 is an frugal number, since it uses more digits than its factorization.

991649505856 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 248966 (or 124479 counting only the distinct ones).

The product of its (nonzero) digits is 104976000, while the sum is 67.

The spelling of 991649505856 in words is "nine hundred ninety-one billion, six hundred forty-nine million, five hundred five thousand, eight hundred fifty-six".