21212387 has 8 divisors (see below), whose sum is σ = 24288000. Its totient is φ = 18148104.

The previous prime is 21212353. The next prime is 21212423. The reversal of 21212387 is 78321212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21212387 - 2⁸ = 21212131 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21212887) 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 7 ways as a sum of consecutive naturals, for example, 1664 + ... + 6722.

It is an arithmetic number, because the mean of its divisors is an integer number (3036000).

Almost surely, 2^21212387 is an apocalyptic number.

21212387 is a deficient number, since it is larger than the sum of its proper divisors (3075613).

21212387 is an equidigital number, since it uses as much as digits as its factorization.

21212387 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 5665.

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

The square root of 21212387 is about 4605.6907190996. The cubic root of 21212387 is about 276.8193942315.

Adding to 21212387 its reverse (78321212), we get a palindrome (99533599).

The spelling of 21212387 in words is "twenty-one million, two hundred twelve thousand, three hundred eighty-seven".