21340381 has 2 divisors, whose sum is σ = 21340382. Its totient is φ = 21340380.

The previous prime is 21340373. The next prime is 21340387. The reversal of 21340381 is 18304312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20557156 + 783225 = 4534^2 + 885^2 .

It is a cyclic number.

It is not a de Polignac number, because 21340381 - 2³ = 21340373 is a prime.

It is a super-2 number, since 2×21340381² = 910823722450322, which contains 22 as substring.

It is a Chen prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21340387) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10670190 + 10670191.

It is an arithmetic number, because the mean of its divisors is an integer number (10670191).

Almost surely, 2^21340381 is an apocalyptic number.

It is an amenable number.

21340381 is a deficient number, since it is larger than the sum of its proper divisors (1).

21340381 is an equidigital number, since it uses as much as digits as its factorization.

21340381 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 576, while the sum is 22.

The square root of 21340381 is about 4619.5650228133. The cubic root of 21340381 is about 277.3750474973.

Adding to 21340381 its reverse (18304312), we get a palindrome (39644693).

The spelling of 21340381 in words is "twenty-one million, three hundred forty thousand, three hundred eighty-one".