21253155 has 32 divisors (see below), whose sum is σ = 42398208. Its totient is φ = 8832000.

The previous prime is 21253121. The next prime is 21253181. The reversal of 21253155 is 55135212.

It is a happy number.

It is not a de Polignac number, because 21253155 - 2⁸ = 21252899 is a prime.

It is a super-3 number, since 3×21253155³ (a number of 23 digits) contains 333 as substring.

It is an unprimeable number.

It is a polite number, since it can be written in 31 ways as a sum of consecutive naturals, for example, 8046 + ... + 10355.

It is an arithmetic number, because the mean of its divisors is an integer number (1324944).

Almost surely, 2^21253155 is an apocalyptic number.

21253155 is a deficient number, since it is larger than the sum of its proper divisors (21145053).

21253155 is a wasteful number, since it uses less digits than its factorization.

21253155 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 18427.

The product of its digits is 1500, while the sum is 24.

The square root of 21253155 is about 4610.1144237426. The cubic root of 21253155 is about 276.9966200980.

Adding to 21253155 its reverse (55135212), we get a palindrome (76388367).

The spelling of 21253155 in words is "twenty-one million, two hundred fifty-three thousand, one hundred fifty-five".