21041381 has 2 divisors, whose sum is σ = 21041382. Its totient is φ = 21041380.

The previous prime is 21041369. The next prime is 21041387. The reversal of 21041381 is 18314012.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 16240900 + 4800481 = 4030^2 + 2191^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21041381 is a prime.

It is a super-2 number, since 2×21041381² = 885479428774322, which contains 22 as substring.

It is a Sophie Germain prime.

It is a Curzon number.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21041387) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10520690 + 10520691.

It is an arithmetic number, because the mean of its divisors is an integer number (10520691).

Almost surely, 2^21041381 is an apocalyptic number.

It is an amenable number.

21041381 is a deficient number, since it is larger than the sum of its proper divisors (1).

21041381 is an equidigital number, since it uses as much as digits as its factorization.

21041381 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 192, while the sum is 20.

The square root of 21041381 is about 4587.0885101554. The cubic root of 21041381 is about 276.0735162630.

Adding to 21041381 its reverse (18314012), we get a palindrome (39355393).

The spelling of 21041381 in words is "twenty-one million, forty-one thousand, three hundred eighty-one".