21024387 has 8 divisors (see below), whose sum is σ = 31147280. Its totient is φ = 14016240.

The previous prime is 21024379. The next prime is 21024389. The reversal of 21024387 is 78342012.

It is not a de Polignac number, because 21024387 - 2³ = 21024379 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 778681 = 21024387 / (2 + 1 + 0 + 2 + 4 + 3 + 8 + 7).

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21024387.

It is not an unprimeable number, because it can be changed into a prime (21024389) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 389314 + ... + 389367.

It is an arithmetic number, because the mean of its divisors is an integer number (3893410).

Almost surely, 2^21024387 is an apocalyptic number.

21024387 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21024387 is a deficient number, since it is larger than the sum of its proper divisors (10122893).

21024387 is an equidigital number, since it uses as much as digits as its factorization.

21024387 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 778690 (or 778684 counting only the distinct ones).

The product of its (nonzero) digits is 2688, while the sum is 27.

The square root of 21024387 is about 4585.2357627498. The cubic root of 21024387 is about 275.9991729654. Note that the first 3 decimals are identical.

Adding to 21024387 its reverse (78342012), we get a palindrome (99366399).

The spelling of 21024387 in words is "twenty-one million, twenty-four thousand, three hundred eighty-seven".