21253775 has 12 divisors (see below), whose sum is σ = 26430600. Its totient is φ = 16954080.

The previous prime is 21253763. The next prime is 21253849. The reversal of 21253775 is 57735212.

It is not a de Polignac number, because 21253775 - 2⁴ = 21253759 is a prime.

It is a hoax number, since the sum of its digits (32) coincides with the sum of the digits of its distinct prime factors.

It is a congruent number.

It is an unprimeable number.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 9461 + ... + 11489.

It is an arithmetic number, because the mean of its divisors is an integer number (2202550).

Almost surely, 2^21253775 is an apocalyptic number.

21253775 is a gapful number since it is divisible by the number (25) formed by its first and last digit.

21253775 is a deficient number, since it is larger than the sum of its proper divisors (5176825).

21253775 is a wasteful number, since it uses less digits than its factorization.

21253775 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 2458 (or 2453 counting only the distinct ones).

The product of its digits is 14700, while the sum is 32.

The square root of 21253775 is about 4610.1816667025. The cubic root of 21253775 is about 276.9993135998. Note that the first 3 decimals are identical.

Adding to 21253775 its reverse (57735212), we get a palindrome (78988987).

The spelling of 21253775 in words is "twenty-one million, two hundred fifty-three thousand, seven hundred seventy-five".