21808087 has 24 divisors (see below), whose sum is σ = 26676000. Its totient is φ = 17752896.

The previous prime is 21808081. The next prime is 21808091. The reversal of 21808087 is 78080812.

It is not a de Polignac number, because 21808087 - 2⁷ = 21807959 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 (21808081) by changing a digit.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 146289 + ... + 146437.

It is an arithmetic number, because the mean of its divisors is an integer number (1111500).

Almost surely, 2^21808087 is an apocalyptic number.

21808087 is a deficient number, since it is larger than the sum of its proper divisors (4867913).

21808087 is a wasteful number, since it uses less digits than its factorization.

21808087 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 295 (or 288 counting only the distinct ones).

The product of its (nonzero) digits is 7168, while the sum is 34.

The square root of 21808087 is about 4669.9129542209. The cubic root of 21808087 is about 279.3867829979.

Adding to 21808087 its reverse (78080812), we get a palindrome (99888899).

The spelling of 21808087 in words is "twenty-one million, eight hundred eight thousand, eighty-seven".