21214381 has 2 divisors, whose sum is σ = 21214382. Its totient is φ = 21214380.

The previous prime is 21214373. The next prime is 21214429. The reversal of 21214381 is 18341212.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20848356 + 366025 = 4566^2 + 605^2 .

It is a cyclic number.

It is not a de Polignac number, because 21214381 - 2³ = 21214373 is a prime.

It is a super-2 number, since 2×21214381² = 900099922426322, which contains 22 as substring.

It is a Chen prime.

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 (21214321) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10607190 + 10607191.

It is an arithmetic number, because the mean of its divisors is an integer number (10607191).

Almost surely, 2^21214381 is an apocalyptic number.

It is an amenable number.

21214381 is a deficient number, since it is larger than the sum of its proper divisors (1).

21214381 is an equidigital number, since it uses as much as digits as its factorization.

21214381 is an odious number, because the sum of its binary digits is odd.

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

The square root of 21214381 is about 4605.9071853436. The cubic root of 21214381 is about 276.8280677890.

Adding to 21214381 its reverse (18341212), we get a palindrome (39555593).

The spelling of 21214381 in words is "twenty-one million, two hundred fourteen thousand, three hundred eighty-one".