21870187 has 8 divisors (see below), whose sum is σ = 22486640. Its totient is φ = 21258720.

The previous prime is 21870169. The next prime is 21870193. The reversal of 21870187 is 78107812.

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

It is a cyclic number.

It is not a de Polignac number, because 21870187 - 2¹¹ = 21868139 is a prime.

It is an alternating number because its digits alternate between even and odd.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21870127) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 8737 + ... + 10957.

It is an arithmetic number, because the mean of its divisors is an integer number (2810830).

Almost surely, 2^21870187 is an apocalyptic number.

21870187 is a deficient number, since it is larger than the sum of its proper divisors (616453).

21870187 is a wasteful number, since it uses less digits than its factorization.

21870187 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 2493.

The product of its (nonzero) digits is 6272, while the sum is 34.

The square root of 21870187 is about 4676.5571738192. The cubic root of 21870187 is about 279.6517225877.

Adding to 21870187 its reverse (78107812), we get a palindrome (99977999).

The spelling of 21870187 in words is "twenty-one million, eight hundred seventy thousand, one hundred eighty-seven".