21004102381 has 2 divisors, whose sum is σ = 21004102382. Its totient is φ = 21004102380.

The previous prime is 21004102363. The next prime is 21004102403. The reversal of 21004102381 is 18320140012.

It is a happy number.

It is an a-pointer prime, because the next prime (21004102403) can be obtained adding 21004102381 to its sum of digits (22).

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20861180356 + 142922025 = 144434^2 + 11955^2 .

It is a cyclic number.

It is not a de Polignac number, because 21004102381 - 2⁹ = 21004101869 is a prime.

It is a super-2 number, since 2×21004102381² (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 (21004102331) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10502051190 + 10502051191.

It is an arithmetic number, because the mean of its divisors is an integer number (10502051191).

Almost surely, 2^21004102381 is an apocalyptic number.

It is an amenable number.

21004102381 is a deficient number, since it is larger than the sum of its proper divisors (1).

21004102381 is an equidigital number, since it uses as much as digits as its factorization.

21004102381 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 384, while the sum is 22.

Adding to 21004102381 its reverse (18320140012), we get a palindrome (39324242393).

The spelling of 21004102381 in words is "twenty-one billion, four million, one hundred two thousand, three hundred eighty-one".