21280587 has 8 divisors (see below), whose sum is σ = 29141136. Its totient is φ = 13803552.

The previous prime is 21280579. The next prime is 21280639. The reversal of 21280587 is 78508212.

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

It is not a de Polignac number, because 21280587 - 2³ = 21280579 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21280547) 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, 95748 + ... + 95969.

It is an arithmetic number, because the mean of its divisors is an integer number (3642642).

Almost surely, 2^21280587 is an apocalyptic number.

21280587 is a deficient number, since it is larger than the sum of its proper divisors (7860549).

21280587 is a wasteful number, since it uses less digits than its factorization.

21280587 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 191757.

The product of its (nonzero) digits is 8960, while the sum is 33.

The square root of 21280587 is about 4613.0886616236. The cubic root of 21280587 is about 277.1157444414.

Adding to 21280587 its reverse (78508212), we get a palindrome (99788799).

The spelling of 21280587 in words is "twenty-one million, two hundred eighty thousand, five hundred eighty-seven".