21000487 has 4 divisors (see below), whose sum is σ = 21512736. Its totient is φ = 20488240.

The previous prime is 21000481. The next prime is 21000509. The reversal of 21000487 is 78400012.

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 21000487 - 2¹⁹ = 20476199 is a prime.

It is a Smith number, since the sum of its digits (22) coincides with the sum of the digits of its prime factors. Since it is squarefree, it is also a hoax number.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21000481) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 256063 + ... + 256144.

It is an arithmetic number, because the mean of its divisors is an integer number (5378184).

Almost surely, 2^21000487 is an apocalyptic number.

21000487 is a deficient number, since it is larger than the sum of its proper divisors (512249).

21000487 is an equidigital number, since it uses as much as digits as its factorization.

21000487 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 512248.

The product of its (nonzero) digits is 448, while the sum is 22.

The square root of 21000487 is about 4582.6288307041. The cubic root of 21000487 is about 275.8945503138.

Adding to 21000487 its reverse (78400012), we get a palindrome (99400499).

The spelling of 21000487 in words is "twenty-one million, four hundred eighty-seven", and thus it is an aban number.