21107381 has 2 divisors, whose sum is σ = 21107382. Its totient is φ = 21107380.

The previous prime is 21107369. The next prime is 21107393. The reversal of 21107381 is 18370112.

It is a happy number.

It is a balanced prime because it is at equal distance from previous prime (21107369) and next prime (21107393).

It can be written as a sum of positive squares in only one way, i.e., 18576100 + 2531281 = 4310^2 + 1591^2 .

It is a cyclic number.

It is not a de Polignac number, because 21107381 - 2²² = 16913077 is a prime.

It is a super-2 number, since 2×21107381² = 891043065358322, 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 (21107341) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10553690 + 10553691.

It is an arithmetic number, because the mean of its divisors is an integer number (10553691).

Almost surely, 2^21107381 is an apocalyptic number.

It is an amenable number.

21107381 is a deficient number, since it is larger than the sum of its proper divisors (1).

21107381 is an equidigital number, since it uses as much as digits as its factorization.

21107381 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 336, while the sum is 23.

The square root of 21107381 is about 4594.2769833783. The cubic root of 21107381 is about 276.3618660666.

Adding to 21107381 its reverse (18370112), we get a palindrome (39477493).

The spelling of 21107381 in words is "twenty-one million, one hundred seven thousand, three hundred eighty-one".