21194991826 has 4 divisors (see below), whose sum is σ = 31792487742. Its totient is φ = 10597495912.

The previous prime is 21194991817. The next prime is 21194991833. The reversal of 21194991826 is 62819949112.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in only one way, i.e., 21157157025 + 37834801 = 145455^2 + 6151^2 .

It is an unprimeable number.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 5298747955 + ... + 5298747958.

Almost surely, 2^21194991826 is an apocalyptic number.

21194991826 is a deficient number, since it is larger than the sum of its proper divisors (10597495916).

21194991826 is a wasteful number, since it uses less digits than its factorization.

21194991826 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 10597495915.

The product of its digits is 559872, while the sum is 52.

The spelling of 21194991826 in words is "twenty-one billion, one hundred ninety-four million, nine hundred ninety-one thousand, eight hundred twenty-six".