21218886 has 24 divisors (see below), whose sum is σ = 49511280. Its totient is φ = 6528816.

The previous prime is 21218863. The next prime is 21218887. The reversal of 21218886 is 68881212.

It is a super-2 number, since 2×21218886² = 900482246161992, which contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21218886.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21218887) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 45106 + ... + 45573.

It is an arithmetic number, because the mean of its divisors is an integer number (2062970).

Almost surely, 2^21218886 is an apocalyptic number.

21218886 is a gapful number since it is divisible by the number (26) formed by its first and last digit.

21218886 is an abundant number, since it is smaller than the sum of its proper divisors (28292394).

It is a pseudoperfect number, because it is the sum of a subset of its proper divisors.

21218886 is a wasteful number, since it uses less digits than its factorization.

21218886 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 90700 (or 90697 counting only the distinct ones).

The product of its digits is 12288, while the sum is 36.

The square root of 21218886 is about 4606.3962052780. The cubic root of 21218886 is about 276.8476617644.

The spelling of 21218886 in words is "twenty-one million, two hundred eighteen thousand, eight hundred eighty-six".