21541251481 has 2 divisors, whose sum is σ = 21541251482. Its totient is φ = 21541251480.

The previous prime is 21541251467. The next prime is 21541251493. The reversal of 21541251481 is 18415214512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 21256182025 + 285069456 = 145795^2 + 16884^2 .

It is a cyclic number.

It is not a de Polignac number, because 21541251481 - 2⁷ = 21541251353 is a prime.

It is a super-2 number, since 2×21541251481² (a number of 21 digits) contains 22 as substring.

It is not a weakly prime, because it can be changed into another prime (21541251421) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10770625740 + 10770625741.

It is an arithmetic number, because the mean of its divisors is an integer number (10770625741).

Almost surely, 2^21541251481 is an apocalyptic number.

It is an amenable number.

21541251481 is a deficient number, since it is larger than the sum of its proper divisors (1).

21541251481 is an equidigital number, since it uses as much as digits as its factorization.

21541251481 is an evil number, because the sum of its binary digits is even.

The product of its digits is 12800, while the sum is 34.

Adding to 21541251481 its reverse (18415214512), we get a palindrome (39956465993).

The spelling of 21541251481 in words is "twenty-one billion, five hundred forty-one million, two hundred fifty-one thousand, four hundred eighty-one".