21155229 has 8 divisors (see below), whose sum is σ = 31341120. Its totient is φ = 14103468.

The previous prime is 21155219. The next prime is 21155257. The reversal of 21155229 is 92255112.

It is not a de Polignac number, because 21155229 - 2¹³ = 21147037 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27), and also a Moran number because the ratio is a prime number: 783527 = 21155229 / (2 + 1 + 1 + 5 + 5 + 2 + 2 + 9).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21155219) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 391737 + ... + 391790.

It is an arithmetic number, because the mean of its divisors is an integer number (3917640).

Almost surely, 2^21155229 is an apocalyptic number.

It is an amenable number.

21155229 is a deficient number, since it is larger than the sum of its proper divisors (10185891).

21155229 is an equidigital number, since it uses as much as digits as its factorization.

21155229 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 783536 (or 783530 counting only the distinct ones).

The product of its digits is 1800, while the sum is 27.

The square root of 21155229 is about 4599.4813838084. The cubic root of 21155229 is about 276.5705353023.

The spelling of 21155229 in words is "twenty-one million, one hundred fifty-five thousand, two hundred twenty-nine".