21549636 has 36 divisors (see below), whose sum is σ = 55246464. Its totient is φ = 7081200.

The previous prime is 21549623. The next prime is 21549637. The reversal of 21549636 is 63694512.

It is a happy number.

21549636 is a `hidden beast` number, since 2 + 15 + 4 + 9 + 636 = 666.

It is a tau number, because it is divible by the number of its divisors (36).

It is a Harshad number since it is a multiple of its sum of digits (36).

It is a zygodrome in base 3.

It is a self number, because there is not a number n which added to its sum of digits gives 21549636.

It is not an unprimeable number, because it can be changed into a prime (21549637) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 1660 + ... + 6771.

It is an arithmetic number, because the mean of its divisors is an integer number (1534624).

Almost surely, 2^21549636 is an apocalyptic number.

It is an amenable number.

21549636 is an abundant number, since it is smaller than the sum of its proper divisors (33696828).

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

21549636 is a wasteful number, since it uses less digits than its factorization.

21549636 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 8512 (or 8507 counting only the distinct ones).

The product of its digits is 38880, while the sum is 36.

The square root of 21549636 is about 4642.1585496405. The cubic root of 21549636 is about 278.2787088073.

The spelling of 21549636 in words is "twenty-one million, five hundred forty-nine thousand, six hundred thirty-six".