21815055 has 32 divisors (see below), whose sum is σ = 38987520. Its totient is φ = 11573280.

The previous prime is 21815051. The next prime is 21815071. The reversal of 21815055 is 55051812.

It is not a de Polignac number, because 21815055 - 2² = 21815051 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21815051) by changing a digit.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 37920 + ... + 38490.

It is an arithmetic number, because the mean of its divisors is an integer number (1218360).

Almost surely, 2^21815055 is an apocalyptic number.

21815055 is a deficient number, since it is larger than the sum of its proper divisors (17172465).

21815055 is a wasteful number, since it uses less digits than its factorization.

21815055 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 868 (or 862 counting only the distinct ones).

The product of its (nonzero) digits is 2000, while the sum is 27.

The square root of 21815055 is about 4670.6589470866. The cubic root of 21815055 is about 279.4165358720.

Adding to 21815055 its reverse (55051812), we get a palindrome (76866867).

The spelling of 21815055 in words is "twenty-one million, eight hundred fifteen thousand, fifty-five".