21381407 has 2 divisors, whose sum is σ = 21381408. Its totient is φ = 21381406.

The previous prime is 21381389. The next prime is 21381433. The reversal of 21381407 is 70418312.

It is an a-pointer prime, because the next prime (21381433) can be obtained adding 21381407 to its sum of digits (26).

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21381407 - 2¹² = 21377311 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21381457) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10690703 + 10690704.

It is an arithmetic number, because the mean of its divisors is an integer number (10690704).

Almost surely, 2^21381407 is an apocalyptic number.

21381407 is a deficient number, since it is larger than the sum of its proper divisors (1).

21381407 is an equidigital number, since it uses as much as digits as its factorization.

21381407 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 1344, while the sum is 26.

The square root of 21381407 is about 4624.0033520749. The cubic root of 21381407 is about 277.5526810678.

Adding to 21381407 its reverse (70418312), we get a palindrome (91799719).

The spelling of 21381407 in words is "twenty-one million, three hundred eighty-one thousand, four hundred seven".