21253771 has 24 divisors (see below), whose sum is σ = 27885312. Its totient is φ = 15826800.

The previous prime is 21253763. The next prime is 21253849. The reversal of 21253771 is 17735212.

It is not a de Polignac number, because 21253771 - 2³ = 21253763 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21253711) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (11) of ones.

It is a polite number, since it can be written in 23 ways as a sum of consecutive naturals, for example, 18936 + ... + 20026.

It is an arithmetic number, because the mean of its divisors is an integer number (1161888).

Almost surely, 2^21253771 is an apocalyptic number.

21253771 is a deficient number, since it is larger than the sum of its proper divisors (6631541).

21253771 is a wasteful number, since it uses less digits than its factorization.

21253771 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1143 (or 1132 counting only the distinct ones).

The product of its digits is 2940, while the sum is 28.

The square root of 21253771 is about 4610.1812328801. The cubic root of 21253771 is about 276.9992962226. Note that the first 3 decimals are identical.

Adding to 21253771 its reverse (17735212), we get a palindrome (38988983).

The spelling of 21253771 in words is "twenty-one million, two hundred fifty-three thousand, seven hundred seventy-one".