21509452537 has 2 divisors, whose sum is σ = 21509452538. Its totient is φ = 21509452536.

The previous prime is 21509452421. The next prime is 21509452541. The reversal of 21509452537 is 73525490512.

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., 21478661136 + 30791401 = 146556^2 + 5549^2 .

It is a cyclic number.

It is not a de Polignac number, because 21509452537 - 2¹⁵ = 21509419769 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21509452493 and 21509452502.

It is not a weakly prime, because it can be changed into another prime (21501452537) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10754726268 + 10754726269.

It is an arithmetic number, because the mean of its divisors is an integer number (10754726269).

Almost surely, 2^21509452537 is an apocalyptic number.

It is an amenable number.

21509452537 is a deficient number, since it is larger than the sum of its proper divisors (1).

21509452537 is an equidigital number, since it uses as much as digits as its factorization.

21509452537 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 378000, while the sum is 43.

The spelling of 21509452537 in words is "twenty-one billion, five hundred nine million, four hundred fifty-two thousand, five hundred thirty-seven".