21122555 has 4 divisors (see below), whose sum is σ = 25347072. Its totient is φ = 16898040.

The previous prime is 21122473. The next prime is 21122561. The reversal of 21122555 is 55522112.

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

It is not a de Polignac number, because 21122555 - 2¹⁶ = 21057019 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21122555.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2112251 + ... + 2112260.

It is an arithmetic number, because the mean of its divisors is an integer number (6336768).

Almost surely, 2^21122555 is an apocalyptic number.

21122555 is a deficient number, since it is larger than the sum of its proper divisors (4224517).

21122555 is an equidigital number, since it uses as much as digits as its factorization.

21122555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4224516.

The product of its digits is 1000, while the sum is 23.

The square root of 21122555 is about 4595.9280890806. The cubic root of 21122555 is about 276.4280752986.

Adding to 21122555 its reverse (55522112), we get a palindrome (76644667).

The spelling of 21122555 in words is "twenty-one million, one hundred twenty-two thousand, five hundred fifty-five".