21736578687 has 4 divisors (see below), whose sum is σ = 28982104920. Its totient is φ = 14491052456.

The previous prime is 21736578673. The next prime is 21736578719. The reversal of 21736578687 is 78687563712.

It is a happy number.

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

It is a cyclic number.

It is not a de Polignac number, because 21736578687 - 2⁸ = 21736578431 is a prime.

It is a super-2 number, since 2×21736578687² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21736578687.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21736578287) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3622763112 + ... + 3622763117.

It is an arithmetic number, because the mean of its divisors is an integer number (7245526230).

Almost surely, 2^21736578687 is an apocalyptic number.

21736578687 is a deficient number, since it is larger than the sum of its proper divisors (7245526233).

21736578687 is an equidigital number, since it uses as much as digits as its factorization.

21736578687 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7245526232.

The product of its digits is 23708160, while the sum is 60.

The spelling of 21736578687 in words is "twenty-one billion, seven hundred thirty-six million, five hundred seventy-eight thousand, six hundred eighty-seven".