20991209012 has 6 divisors (see below), whose sum is σ = 36734615778. Its totient is φ = 10495604504.

The previous prime is 20991209011. The next prime is 20991209059. The reversal of 20991209012 is 21090219902.

It can be written as a sum of positive squares in only one way, i.e., 20921886736 + 69322276 = 144644^2 + 8326^2 .

It is a super-2 number, since 2×20991209012² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (20991209011) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 2623901123 + ... + 2623901130.

It is an arithmetic number, because the mean of its divisors is an integer number (6122435963).

Almost surely, 2^20991209012 is an apocalyptic number.

It is an amenable number.

20991209012 is a deficient number, since it is larger than the sum of its proper divisors (15743406766).

20991209012 is a wasteful number, since it uses less digits than its factorization.

20991209012 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5247802257 (or 5247802255 counting only the distinct ones).

The product of its (nonzero) digits is 5832, while the sum is 35.

The spelling of 20991209012 in words is "twenty billion, nine hundred ninety-one million, two hundred nine thousand, twelve".