21024987 has 4 divisors (see below), whose sum is σ = 28033320. Its totient is φ = 14016656.

The previous prime is 21024961. The next prime is 21025019. The reversal of 21024987 is 78942012.

It is a happy number.

It is a semiprime because it is the product of two primes.

It is a cyclic number.

It is not a de Polignac number, because 21024987 - 2⁷ = 21024859 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21024907) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 3504162 + ... + 3504167.

It is an arithmetic number, because the mean of its divisors is an integer number (7008330).

Almost surely, 2^21024987 is an apocalyptic number.

21024987 is a deficient number, since it is larger than the sum of its proper divisors (7008333).

21024987 is an equidigital number, since it uses as much as digits as its factorization.

21024987 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7008332.

The product of its (nonzero) digits is 8064, while the sum is 33.

The square root of 21024987 is about 4585.3011896712. The cubic root of 21024987 is about 276.0017984550.

Adding to 21024987 its reverse (78942012), we get a palindrome (99966999).

The spelling of 21024987 in words is "twenty-one million, twenty-four thousand, nine hundred eighty-seven".