21011728081 has 8 divisors (see below), whose sum is σ = 21051607104. Its totient is φ = 20971873200.

The previous prime is 21011728061. The next prime is 21011728097. The reversal of 21011728081 is 18082711012.

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 21011728081 - 2⁷ = 21011727953 is a prime.

It is a super-2 number, since 2×21011728081² (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 (21011728061) 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, 3440931 + ... + 3447031.

It is an arithmetic number, because the mean of its divisors is an integer number (2631450888).

Almost surely, 2^21011728081 is an apocalyptic number.

It is an amenable number.

21011728081 is a deficient number, since it is larger than the sum of its proper divisors (39879023).

21011728081 is an equidigital number, since it uses as much as digits as its factorization.

21011728081 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 12071.

The product of its (nonzero) digits is 1792, while the sum is 31.

The spelling of 21011728081 in words is "twenty-one billion, eleven million, seven hundred twenty-eight thousand, eighty-one".