21550243 has 16 divisors (see below), whose sum is σ = 26008416. Its totient is φ = 17591040.

The previous prime is 21550231. The next prime is 21550253. The reversal of 21550243 is 34205512.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21550243 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21550253) 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 15 ways as a sum of consecutive naturals, for example, 3255 + ... + 7327.

It is an arithmetic number, because the mean of its divisors is an integer number (1625526).

Almost surely, 2^21550243 is an apocalyptic number.

21550243 is a deficient number, since it is larger than the sum of its proper divisors (4458173).

21550243 is a wasteful number, since it uses less digits than its factorization.

21550243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4134.

The product of its (nonzero) digits is 1200, while the sum is 22.

The square root of 21550243 is about 4642.2239282482. The cubic root of 21550243 is about 278.2813215907.

Adding to 21550243 its reverse (34205512), we get a palindrome (55755755).

The spelling of 21550243 in words is "twenty-one million, five hundred fifty thousand, two hundred forty-three".