21002113381 has 2 divisors, whose sum is σ = 21002113382. Its totient is φ = 21002113380.

The previous prime is 21002113367. The next prime is 21002113387. The reversal of 21002113381 is 18331120012.

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., 19833088900 + 1169024481 = 140830^2 + 34191^2 .

It is a cyclic number.

It is not a de Polignac number, because 21002113381 - 2⁹ = 21002112869 is a prime.

It is a super-2 number, since 2×21002113381² (a number of 21 digits) contains 22 as substring.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21002113387) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10501056690 + 10501056691.

It is an arithmetic number, because the mean of its divisors is an integer number (10501056691).

Almost surely, 2^21002113381 is an apocalyptic number.

It is an amenable number.

21002113381 is a deficient number, since it is larger than the sum of its proper divisors (1).

21002113381 is an equidigital number, since it uses as much as digits as its factorization.

21002113381 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 288, while the sum is 22.

Adding to 21002113381 its reverse (18331120012), we get a palindrome (39333233393).

The spelling of 21002113381 in words is "twenty-one billion, two million, one hundred thirteen thousand, three hundred eighty-one".