21544323257 has 2 divisors, whose sum is σ = 21544323258. Its totient is φ = 21544323256.

The previous prime is 21544323179. The next prime is 21544323347. The reversal of 21544323257 is 75232344512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20301690256 + 1242633001 = 142484^2 + 35251^2 .

It is a cyclic number.

It is not a de Polignac number, because 21544323257 - 2⁸ = 21544323001 is a prime.

It is a super-2 number, since 2×21544323257² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21544323257.

It is not a weakly prime, because it can be changed into another prime (21544323557) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10772161628 + 10772161629.

It is an arithmetic number, because the mean of its divisors is an integer number (10772161629).

Almost surely, 2^21544323257 is an apocalyptic number.

It is an amenable number.

21544323257 is a deficient number, since it is larger than the sum of its proper divisors (1).

21544323257 is an equidigital number, since it uses as much as digits as its factorization.

21544323257 is an evil number, because the sum of its binary digits is even.

The product of its digits is 201600, while the sum is 38.

Adding to 21544323257 its reverse (75232344512), we get a palindrome (96776667769).

The spelling of 21544323257 in words is "twenty-one billion, five hundred forty-four million, three hundred twenty-three thousand, two hundred fifty-seven".