21550355 has 4 divisors (see below), whose sum is σ = 25860432. Its totient is φ = 17240280.

The previous prime is 21550337. The next prime is 21550357. The reversal of 21550355 is 55305512.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21550355 - 2⁸ = 21550099 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21550357) 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, 2155031 + ... + 2155040.

It is an arithmetic number, because the mean of its divisors is an integer number (6465108).

Almost surely, 2^21550355 is an apocalyptic number.

21550355 is a deficient number, since it is larger than the sum of its proper divisors (4310077).

21550355 is an equidigital number, since it uses as much as digits as its factorization.

21550355 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4310076.

The product of its (nonzero) digits is 3750, while the sum is 26.

The square root of 21550355 is about 4642.2359914162. The cubic root of 21550355 is about 278.2818036804.

Adding to 21550355 its reverse (55305512), we get a palindrome (76855867).

The spelling of 21550355 in words is "twenty-one million, five hundred fifty thousand, three hundred fifty-five".