21422381 has 2 divisors, whose sum is σ = 21422382. Its totient is φ = 21422380.

The previous prime is 21422347. The next prime is 21422399. The reversal of 21422381 is 18322412.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 17682025 + 3740356 = 4205^2 + 1934^2 .

It is a cyclic number.

It is not a de Polignac number, because 21422381 - 2¹⁴ = 21405997 is a prime.

It is a super-2 number, since 2×21422381² = 917836815418322, 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 (21422321) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10711190 + 10711191.

It is an arithmetic number, because the mean of its divisors is an integer number (10711191).

Almost surely, 2^21422381 is an apocalyptic number.

It is an amenable number.

21422381 is a deficient number, since it is larger than the sum of its proper divisors (1).

21422381 is an equidigital number, since it uses as much as digits as its factorization.

21422381 is an evil number, because the sum of its binary digits is even.

The product of its digits is 768, while the sum is 23.

The square root of 21422381 is about 4628.4318078589. The cubic root of 21422381 is about 277.7298628406.

Adding to 21422381 its reverse (18322412), we get a palindrome (39744793).

The spelling of 21422381 in words is "twenty-one million, four hundred twenty-two thousand, three hundred eighty-one".