21118887 has 24 divisors (see below), whose sum is σ = 31855824. Its totient is φ = 13981248.

The previous prime is 21118883. The next prime is 21118901. The reversal of 21118887 is 78881112.

It is not a de Polignac number, because 21118887 - 2² = 21118883 is a prime.

It is a Smith number, since the sum of its digits (36) coincides with the sum of the digits of its prime factors.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21118883) 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, 56433 + ... + 56805.

It is an arithmetic number, because the mean of its divisors is an integer number (1327326).

Almost surely, 2^21118887 is an apocalyptic number.

21118887 is a gapful number since it is divisible by the number (27) formed by its first and last digit.

21118887 is a deficient number, since it is larger than the sum of its proper divisors (10736937).

21118887 is an equidigital number, since it uses as much as digits as its factorization.

21118887 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 621 (or 609 counting only the distinct ones).

The product of its digits is 7168, while the sum is 36.

The square root of 21118887 is about 4595.5290228656. The cubic root of 21118887 is about 276.4120734958.

Adding to 21118887 its reverse (78881112), we get a palindrome (99999999).

The spelling of 21118887 in words is "twenty-one million, one hundred eighteen thousand, eight hundred eighty-seven".