21011155481 has 2 divisors, whose sum is σ = 21011155482. Its totient is φ = 21011155480.

The previous prime is 21011155471. The next prime is 21011155483. The reversal of 21011155481 is 18455111012.

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., 20864358025 + 146797456 = 144445^2 + 12116^2 .

It is a cyclic number.

It is not a de Polignac number, because 21011155481 - 2²² = 21006961177 is a prime.

It is a super-2 number, since 2×21011155481² (a number of 21 digits) contains 22 as substring.

Together with 21011155483, it forms a pair of twin primes.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21011155483) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10505577740 + 10505577741.

It is an arithmetic number, because the mean of its divisors is an integer number (10505577741).

Almost surely, 2^21011155481 is an apocalyptic number.

It is an amenable number.

21011155481 is a deficient number, since it is larger than the sum of its proper divisors (1).

21011155481 is an equidigital number, since it uses as much as digits as its factorization.

21011155481 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1600, while the sum is 29.

Adding to 21011155481 its reverse (18455111012), we get a palindrome (39466266493).

The spelling of 21011155481 in words is "twenty-one billion, eleven million, one hundred fifty-five thousand, four hundred eighty-one".