21568684723 has 4 divisors (see below), whose sum is σ = 22506453648. Its totient is φ = 20630915800.

The previous prime is 21568684637. The next prime is 21568684729. The reversal of 21568684723 is 32748686512.

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 21568684723 - 2¹³ = 21568676531 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21568684729) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 468884428 + ... + 468884473.

It is an arithmetic number, because the mean of its divisors is an integer number (5626613412).

Almost surely, 2^21568684723 is an apocalyptic number.

21568684723 is a gapful number since it is divisible by the number (23) formed by its first and last digit.

21568684723 is a deficient number, since it is larger than the sum of its proper divisors (937768925).

21568684723 is an equidigital number, since it uses as much as digits as its factorization.

21568684723 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 937768924.

The product of its digits is 3870720, while the sum is 52.

The spelling of 21568684723 in words is "twenty-one billion, five hundred sixty-eight million, six hundred eighty-four thousand, seven hundred twenty-three".