21921505537 has 2 divisors, whose sum is σ = 21921505538. Its totient is φ = 21921505536.

The previous prime is 21921505513. The next prime is 21921505561. The reversal of 21921505537 is 73550512912.

It is a balanced prime because it is at equal distance from previous prime (21921505513) and next prime (21921505561).

It can be written as a sum of positive squares in only one way, i.e., 15090648336 + 6830857201 = 122844^2 + 82649^2 .

It is a cyclic number.

It is not a de Polignac number, because 21921505537 - 2³¹ = 19774021889 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21921505537.

It is not a weakly prime, because it can be changed into another prime (21921505577) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10960752768 + 10960752769.

It is an arithmetic number, because the mean of its divisors is an integer number (10960752769).

Almost surely, 2^21921505537 is an apocalyptic number.

It is an amenable number.

21921505537 is a deficient number, since it is larger than the sum of its proper divisors (1).

21921505537 is an equidigital number, since it uses as much as digits as its factorization.

21921505537 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 94500, while the sum is 40.

The spelling of 21921505537 in words is "twenty-one billion, nine hundred twenty-one million, five hundred five thousand, five hundred thirty-seven".