21089388 has 12 divisors (see below), whose sum is σ = 49208600. Its totient is φ = 7029792.

The previous prime is 21089381. The next prime is 21089407. The reversal of 21089388 is 88398012.

It is a tau number, because it is divible by the number of its divisors (12).

It is not an unprimeable number, because it can be changed into a prime (21089381) 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 3 ways as a sum of consecutive naturals, for example, 878713 + ... + 878736.

Almost surely, 2^21089388 is an apocalyptic number.

It is an amenable number.

21089388 is an abundant number, since it is smaller than the sum of its proper divisors (28119212).

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

21089388 is a wasteful number, since it uses less digits than its factorization.

21089388 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1757456 (or 1757454 counting only the distinct ones).

The product of its (nonzero) digits is 27648, while the sum is 39.

The square root of 21089388 is about 4592.3183687545. The cubic root of 21089388 is about 276.2833154609.

It can be divided in two parts, 210 and 89388, that added together give a palindrome (89598).

The spelling of 21089388 in words is "twenty-one million, eighty-nine thousand, three hundred eighty-eight".