21861087 has 4 divisors (see below), whose sum is σ = 29148120. Its totient is φ = 14574056.

The previous prime is 21861083. The next prime is 21861097. The reversal of 21861087 is 78016812.

It is a happy number.

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 21861087 - 2² = 21861083 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21861083) 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, 3643512 + ... + 3643517.

It is an arithmetic number, because the mean of its divisors is an integer number (7287030).

Almost surely, 2^21861087 is an apocalyptic number.

21861087 is a deficient number, since it is larger than the sum of its proper divisors (7287033).

21861087 is an equidigital number, since it uses as much as digits as its factorization.

21861087 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7287032.

The product of its (nonzero) digits is 5376, while the sum is 33.

The square root of 21861087 is about 4675.5841346296. The cubic root of 21861087 is about 279.6129303006.

Adding to 21861087 its reverse (78016812), we get a palindrome (99877899).

The spelling of 21861087 in words is "twenty-one million, eight hundred sixty-one thousand, eighty-seven".