21636386551 has 4 divisors (see below), whose sum is σ = 23300723992. Its totient is φ = 19972049112.

The previous prime is 21636386539. The next prime is 21636386579. The reversal of 21636386551 is 15568363612.

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

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21636386551 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21636386951) 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 in 3 ways as a sum of consecutive naturals, for example, 832168701 + ... + 832168726.

It is an arithmetic number, because the mean of its divisors is an integer number (5825180998).

Almost surely, 2^21636386551 is an apocalyptic number.

21636386551 is a deficient number, since it is larger than the sum of its proper divisors (1664337441).

21636386551 is a wasteful number, since it uses less digits than its factorization.

21636386551 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1664337440.

The product of its digits is 777600, while the sum is 46.

The spelling of 21636386551 in words is "twenty-one billion, six hundred thirty-six million, three hundred eighty-six thousand, five hundred fifty-one".