21728609281 has 8 divisors (see below), whose sum is σ = 22496287680. Its totient is φ = 20962158672.

The previous prime is 21728609269. The next prime is 21728609297. The reversal of 21728609281 is 18290682712.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21728609281 - 2⁷ = 21728609153 is a prime.

It is a super-2 number, since 2×21728609281² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21728600281) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 270855 + ... + 341788.

It is an arithmetic number, because the mean of its divisors is an integer number (2812035960).

Almost surely, 2^21728609281 is an apocalyptic number.

It is an amenable number.

21728609281 is a deficient number, since it is larger than the sum of its proper divisors (767678399).

21728609281 is a wasteful number, since it uses less digits than its factorization.

21728609281 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 613895.

The product of its (nonzero) digits is 193536, while the sum is 46.

The spelling of 21728609281 in words is "twenty-one billion, seven hundred twenty-eight million, six hundred nine thousand, two hundred eighty-one".