21321387 has 10 divisors (see below), whose sum is σ = 31850588. Its totient is φ = 14214204.

The previous prime is 21321379. The next prime is 21321407. The reversal of 21321387 is 78312312.

It is not a de Polignac number, because 21321387 - 2³ = 21321379 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a Duffinian number.

It is a plaindrome in base 16.

It is a self number, because there is not a number n which added to its sum of digits gives 21321387.

It is not an unprimeable number, because it can be changed into a prime (21321337) 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 9 ways as a sum of consecutive naturals, for example, 131533 + ... + 131694.

Almost surely, 2^21321387 is an apocalyptic number.

21321387 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21321387 is a deficient number, since it is larger than the sum of its proper divisors (10529201).

21321387 is an equidigital number, since it uses as much as digits as its factorization.

21321387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 263239 (or 263230 counting only the distinct ones).

The product of its digits is 2016, while the sum is 27.

The square root of 21321387 is about 4617.5087439008. The cubic root of 21321387 is about 277.2927305432.

Adding to 21321387 its reverse (78312312), we get a palindrome (99633699).

The spelling of 21321387 in words is "twenty-one million, three hundred twenty-one thousand, three hundred eighty-seven".