21655416043237 has 2 divisors, whose sum is σ = 21655416043238. Its totient is φ = 21655416043236.

The previous prime is 21655416043207. The next prime is 21655416043273. The reversal of 21655416043237 is 73234061455612.

Together with next prime (21655416043273) it forms an Ormiston pair, because they use the same digits, order apart.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 11688015663076 + 9967400380161 = 3418774^2 + 3157119^2 .

It is a cyclic number.

It is not a de Polignac number, because 21655416043237 - 2¹⁵ = 21655416010469 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21655416043207) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (23) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10827708021618 + 10827708021619.

It is an arithmetic number, because the mean of its divisors is an integer number (10827708021619).

Almost surely, 2^{21655416043237} is an apocalyptic number.

It is an amenable number.

21655416043237 is a deficient number, since it is larger than the sum of its proper divisors (1).

21655416043237 is an equidigital number, since it uses as much as digits as its factorization.

21655416043237 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 3628800, while the sum is 49.

Adding to 21655416043237 its reverse (73234061455612), we get a palindrome (94889477498849).

The spelling of 21655416043237 in words is "twenty-one trillion, six hundred fifty-five billion, four hundred sixteen million, forty-three thousand, two hundred thirty-seven".