21235526581 has 2 divisors, whose sum is σ = 21235526582. Its totient is φ = 21235526580.

The previous prime is 21235526563. The next prime is 21235526621. The reversal of 21235526581 is 18562553212.

It is an a-pointer prime, because the next prime (21235526621) can be obtained adding 21235526581 to its sum of digits (40).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18400922500 + 2834604081 = 135650^2 + 53241^2 .

It is a cyclic number.

It is not a de Polignac number, because 21235526581 - 2¹⁹ = 21235002293 is a prime.

It is a super-2 number, since 2×21235526581² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21235527581) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10617763290 + 10617763291.

It is an arithmetic number, because the mean of its divisors is an integer number (10617763291).

Almost surely, 2^21235526581 is an apocalyptic number.

It is an amenable number.

21235526581 is a deficient number, since it is larger than the sum of its proper divisors (1).

21235526581 is an equidigital number, since it uses as much as digits as its factorization.

21235526581 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 144000, while the sum is 40.

The spelling of 21235526581 in words is "twenty-one billion, two hundred thirty-five million, five hundred twenty-six thousand, five hundred eighty-one".