21227555 has 4 divisors (see below), whose sum is σ = 25473072. Its totient is φ = 16982040.

The previous prime is 21227533. The next prime is 21227561. The reversal of 21227555 is 55572212.

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

It is not a de Polignac number, because 21227555 - 2¹⁰ = 21226531 is a prime.

It is a Duffinian number.

It is an unprimeable number.

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, 2122751 + ... + 2122760.

It is an arithmetic number, because the mean of its divisors is an integer number (6368268).

Almost surely, 2^21227555 is an apocalyptic number.

21227555 is a deficient number, since it is larger than the sum of its proper divisors (4245517).

21227555 is an equidigital number, since it uses as much as digits as its factorization.

21227555 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4245516.

The product of its digits is 7000, while the sum is 29.

The square root of 21227555 is about 4607.3370833921. The cubic root of 21227555 is about 276.8853587735.

Adding to 21227555 its reverse (55572212), we get a palindrome (76799767).

The spelling of 21227555 in words is "twenty-one million, two hundred twenty-seven thousand, five hundred fifty-five".