21008087 has 4 divisors (see below), whose sum is σ = 21404520. Its totient is φ = 20611656.

The previous prime is 21008083. The next prime is 21008149. The reversal of 21008087 is 78080012.

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 21008087 - 2² = 21008083 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21008081) 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, 198137 + ... + 198242.

It is an arithmetic number, because the mean of its divisors is an integer number (5351130).

Almost surely, 2^21008087 is an apocalyptic number.

21008087 is a deficient number, since it is larger than the sum of its proper divisors (396433).

21008087 is an equidigital number, since it uses as much as digits as its factorization.

21008087 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 396432.

The product of its (nonzero) digits is 896, while the sum is 26.

The square root of 21008087 is about 4583.4579740628. The cubic root of 21008087 is about 275.9278280451.

Adding to 21008087 its reverse (78080012), we get a palindrome (99088099).

The spelling of 21008087 in words is "twenty-one million, eight thousand, eighty-seven".