21243387 has 32 divisors (see below), whose sum is σ = 34456320. Its totient is φ = 11473920.

The previous prime is 21243361. The next prime is 21243403. The reversal of 21243387 is 78334212.

It is not a de Polignac number, because 21243387 - 2⁷ = 21243259 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21243307) 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 in 31 ways as a sum of consecutive naturals, for example, 9663 + ... + 11655.

It is an arithmetic number, because the mean of its divisors is an integer number (1076760).

Almost surely, 2^21243387 is an apocalyptic number.

21243387 is a deficient number, since it is larger than the sum of its proper divisors (13212933).

21243387 is a wasteful number, since it uses less digits than its factorization.

21243387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2043.

The product of its digits is 8064, while the sum is 30.

The square root of 21243387 is about 4609.0548922746. The cubic root of 21243387 is about 276.9541774959.

Adding to 21243387 its reverse (78334212), we get a palindrome (99577599).

The spelling of 21243387 in words is "twenty-one million, two hundred forty-three thousand, three hundred eighty-seven".