21018887 has 4 divisors (see below), whose sum is σ = 21028080. Its totient is φ = 21009696.

The previous prime is 21018869. The next prime is 21018929. The reversal of 21018887 is 78881012.

It is a semiprime because it is the product of two primes, and also a brilliant number, because the two primes have the same length.

It is a cyclic number.

It is not a de Polignac number, because 21018887 - 2⁸ = 21018631 is a prime.

It is a super-2 number, since 2×21018887² = 883587221437538, which contains 22 as substring.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21018857) 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, 1814 + ... + 6732.

It is an arithmetic number, because the mean of its divisors is an integer number (5257020).

Almost surely, 2^21018887 is an apocalyptic number.

21018887 is a deficient number, since it is larger than the sum of its proper divisors (9193).

21018887 is an equidigital number, since it uses as much as digits as its factorization.

21018887 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 9192.

The product of its (nonzero) digits is 7168, while the sum is 35.

The square root of 21018887 is about 4584.6359724628. The cubic root of 21018887 is about 275.9751036494.

Adding to 21018887 its reverse (78881012), we get a palindrome (99899899).

The spelling of 21018887 in words is "twenty-one million, eighteen thousand, eight hundred eighty-seven".