21027728581 has 16 divisors (see below), whose sum is σ = 21889244160. Its totient is φ = 20175644160.

The previous prime is 21027728551. The next prime is 21027728609. The reversal of 21027728581 is 18582772012.

It is a cyclic number.

It is not a de Polignac number, because 21027728581 - 2¹⁷ = 21027597509 is a prime.

It is a super-2 number, since 2×21027728581² (a number of 21 digits) contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21027728531) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 4078101 + ... + 4083253.

It is an arithmetic number, because the mean of its divisors is an integer number (1368077760).

Almost surely, 2^21027728581 is an apocalyptic number.

It is an amenable number.

21027728581 is a deficient number, since it is larger than the sum of its proper divisors (861515579).

21027728581 is a wasteful number, since it uses less digits than its factorization.

21027728581 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 6036.

The product of its (nonzero) digits is 125440, while the sum is 43.

The spelling of 21027728581 in words is "twenty-one billion, twenty-seven million, seven hundred twenty-eight thousand, five hundred eighty-one".