21439387 has 2 divisors, whose sum is σ = 21439388. Its totient is φ = 21439386.

The previous prime is 21439343. The next prime is 21439393. The reversal of 21439387 is 78393412.

It is a strong prime.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21439387 is a prime.

It is a Chen prime.

It is not a weakly prime, because it can be changed into another prime (21439307) by changing a digit.

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

It is a good prime.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10719693 + 10719694.

It is an arithmetic number, because the mean of its divisors is an integer number (10719694).

Almost surely, 2^21439387 is an apocalyptic number.

21439387 is a deficient number, since it is larger than the sum of its proper divisors (1).

21439387 is an equidigital number, since it uses as much as digits as its factorization.

21439387 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 36288, while the sum is 37.

The square root of 21439387 is about 4630.2685667248. The cubic root of 21439387 is about 277.8033346738.

It can be divided in two parts, 214 and 39387, that added together give a square (39601 = 199²).

The spelling of 21439387 in words is "twenty-one million, four hundred thirty-nine thousand, three hundred eighty-seven".