21230555 has 4 divisors (see below), whose sum is σ = 25476672. Its totient is φ = 16984440.

The previous prime is 21230551. The next prime is 21230557. The reversal of 21230555 is 55503212.

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

It is not a de Polignac number, because 21230555 - 2² = 21230551 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 21230555.

It is not an unprimeable number, because it can be changed into a prime (21230551) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2123051 + ... + 2123060.

It is an arithmetic number, because the mean of its divisors is an integer number (6369168).

Almost surely, 2^21230555 is an apocalyptic number.

21230555 is a deficient number, since it is larger than the sum of its proper divisors (4246117).

21230555 is an equidigital number, since it uses as much as digits as its factorization.

21230555 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4246116.

The product of its (nonzero) digits is 1500, while the sum is 23.

The square root of 21230555 is about 4607.6626395603. The cubic root of 21230555 is about 276.8984018355.

Adding to 21230555 its reverse (55503212), we get a palindrome (76733767).

The spelling of 21230555 in words is "twenty-one million, two hundred thirty thousand, five hundred fifty-five".