21531645089 has 2 divisors, whose sum is σ = 21531645090. Its totient is φ = 21531645088.

The previous prime is 21531645071. The next prime is 21531645173. The reversal of 21531645089 is 98054613512.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17163096064 + 4368549025 = 131008^2 + 66095^2 .

It is a cyclic number.

It is not a de Polignac number, because 21531645089 - 2²⁰ = 21530596513 is a prime.

It is a super-2 number, since 2×21531645089² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21531645589) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10765822544 + 10765822545.

It is an arithmetic number, because the mean of its divisors is an integer number (10765822545).

Almost surely, 2^21531645089 is an apocalyptic number.

It is an amenable number.

21531645089 is a deficient number, since it is larger than the sum of its proper divisors (1).

21531645089 is an equidigital number, since it uses as much as digits as its factorization.

21531645089 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 259200, while the sum is 44.

The spelling of 21531645089 in words is "twenty-one billion, five hundred thirty-one million, six hundred forty-five thousand, eighty-nine".