21340387 has 2 divisors, whose sum is σ = 21340388. Its totient is φ = 21340386.

The previous prime is 21340381. The next prime is 21340409. The reversal of 21340387 is 78304312.

21340387 is nontrivially palindromic in base 12.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21340387 - 2¹⁹ = 20816099 is a prime.

It is not a weakly prime, because it can be changed into another prime (21340381) 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, 10670193 + 10670194.

It is an arithmetic number, because the mean of its divisors is an integer number (10670194).

Almost surely, 2^21340387 is an apocalyptic number.

21340387 is a deficient number, since it is larger than the sum of its proper divisors (1).

21340387 is an equidigital number, since it uses as much as digits as its factorization.

21340387 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 4032, while the sum is 28.

The square root of 21340387 is about 4619.5656722250. The cubic root of 21340387 is about 277.3750734926.

Adding to 21340387 its reverse (78304312), we get a palindrome (99644699).

The spelling of 21340387 in words is "twenty-one million, three hundred forty thousand, three hundred eighty-seven".