21550236 has 12 divisors (see below), whose sum is σ = 50283912. Its totient is φ = 7183408.

The previous prime is 21550231. The next prime is 21550253. The reversal of 21550236 is 63205512.

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

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21550231) 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, 897915 + ... + 897938.

It is an arithmetic number, because the mean of its divisors is an integer number (4190326).

Almost surely, 2^21550236 is an apocalyptic number.

It is an amenable number.

21550236 is an abundant number, since it is smaller than the sum of its proper divisors (28733676).

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

21550236 is a wasteful number, since it uses less digits than its factorization.

21550236 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1795860 (or 1795858 counting only the distinct ones).

The product of its (nonzero) digits is 1800, while the sum is 24.

The square root of 21550236 is about 4642.2231742991. The cubic root of 21550236 is about 278.2812914600.

Adding to 21550236 its reverse (63205512), we get a palindrome (84755748).

The spelling of 21550236 in words is "twenty-one million, five hundred fifty thousand, two hundred thirty-six".