21814381 has 2 divisors, whose sum is σ = 21814382. Its totient is φ = 21814380.

The previous prime is 21814379. The next prime is 21814399. The reversal of 21814381 is 18341812.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 19758025 + 2056356 = 4445^2 + 1434^2 .

It is a cyclic number.

It is not a de Polignac number, because 21814381 - 2¹ = 21814379 is a prime.

It is a super-2 number, since 2×21814381² = 951734436826322, which contains 22 as substring.

Together with 21814379, it forms a pair of twin primes.

It is an alternating number because its digits alternate between even and odd.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21814321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10907190 + 10907191.

It is an arithmetic number, because the mean of its divisors is an integer number (10907191).

Almost surely, 2^21814381 is an apocalyptic number.

It is an amenable number.

21814381 is a deficient number, since it is larger than the sum of its proper divisors (1).

21814381 is an equidigital number, since it uses as much as digits as its factorization.

21814381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 1536, while the sum is 28.

The square root of 21814381 is about 4670.5867939693. The cubic root of 21814381 is about 279.4136582158.

The spelling of 21814381 in words is "twenty-one million, eight hundred fourteen thousand, three hundred eighty-one".