10991538991801 has 3 divisors (see below), whose sum is σ = 10991542307151. Its totient is φ = 10991535676452.

The previous prime is 10991538991787. The next prime is 10991538991841. The reversal of 10991538991801 is 10819983519901.

It is a happy number.

The square root of 10991538991801 is 3315349.

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

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It can be written as a sum of positive squares in only one way, i.e., 271546252201 + 10719992739600 = 521101^2 + 3274140^2 .

It is not a de Polignac number, because 10991538991801 - 2⁷ = 10991538991673 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (10991538991841) 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, 1657675 + ... + 4973023.

It is an arithmetic number, because the mean of its divisors is an integer number (3663847435717).

Almost surely, 2^{10991538991801} is an apocalyptic number.

10991538991801 is the 3315349-th square number.

10991538991801 is the 1657675-th centered octagonal number.

It is an amenable number.

10991538991801 is a deficient number, since it is larger than the sum of its proper divisors (3315350).

10991538991801 is an frugal number, since it uses more digits than its factorization.

10991538991801 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6630698 (or 3315349 counting only the distinct ones).

The product of its (nonzero) digits is 6298560, while the sum is 64.

Multiplying 10991538991801 by its sum of digits (64), we get a square (703458495475264 = 26522792²).

It can be divided in two parts, 1099 and 1538991801, that added together give a square (1538992900 = 39230²).

The spelling of 10991538991801 in words is "ten trillion, nine hundred ninety-one billion, five hundred thirty-eight million, nine hundred ninety-one thousand, eight hundred one".