21451001532509 has 2 divisors, whose sum is σ = 21451001532510. Its totient is φ = 21451001532508.

The previous prime is 21451001532391. The next prime is 21451001532511. The reversal of 21451001532509 is 90523510015412.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21447550322500 + 3451210009 = 4631150^2 + 58747^2 .

It is a cyclic number.

It is not a de Polignac number, because 21451001532509 - 2²⁰ = 21451000483933 is a prime.

It is a super-3 number, since 3×21451001532509³ (a number of 41 digits) contains 333 as substring.

Together with 21451001532511, it forms a pair of twin primes.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21451001532529) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10725500766254 + 10725500766255.

It is an arithmetic number, because the mean of its divisors is an integer number (10725500766255).

Almost surely, 2^{21451001532509} is an apocalyptic number.

It is an amenable number.

21451001532509 is a deficient number, since it is larger than the sum of its proper divisors (1).

21451001532509 is an equidigital number, since it uses as much as digits as its factorization.

21451001532509 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 54000, while the sum is 38.

The spelling of 21451001532509 in words is "twenty-one trillion, four hundred fifty-one billion, one million, five hundred thirty-two thousand, five hundred nine".