21447723657 has 4 divisors (see below), whose sum is σ = 28596964880. Its totient is φ = 14298482436.

The previous prime is 21447723637. The next prime is 21447723683. The reversal of 21447723657 is 75632774412.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is not a de Polignac number, because 21447723657 - 2⁶ = 21447723593 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21447723607) 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, 3574620607 + ... + 3574620612.

It is an arithmetic number, because the mean of its divisors is an integer number (7149241220).

Almost surely, 2^21447723657 is an apocalyptic number.

It is an amenable number.

21447723657 is a deficient number, since it is larger than the sum of its proper divisors (7149241223).

21447723657 is an equidigital number, since it uses as much as digits as its factorization.

21447723657 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7149241222.

The product of its digits is 1975680, while the sum is 48.

The spelling of 21447723657 in words is "twenty-one billion, four hundred forty-seven million, seven hundred twenty-three thousand, six hundred fifty-seven".