21253603 has 6 divisors (see below), whose sum is σ = 24723636. Its totient is φ = 18217332.

The previous prime is 21253597. The next prime is 21253613. The reversal of 21253603 is 30635212.

It is a de Polignac number, because none of the positive numbers 2^k-21253603 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21253613) by changing a digit.

It is a polite number, since it can be written in 5 ways as a sum of consecutive naturals, for example, 216825 + ... + 216922.

It is an arithmetic number, because the mean of its divisors is an integer number (4120606).

Almost surely, 2^21253603 is an apocalyptic number.

21253603 is a deficient number, since it is larger than the sum of its proper divisors (3470033).

21253603 is an equidigital number, since it uses as much as digits as its factorization.

21253603 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 433761 (or 433754 counting only the distinct ones).

The product of its (nonzero) digits is 1080, while the sum is 22.

The square root of 21253603 is about 4610.1630123023. The cubic root of 21253603 is about 276.9985663756.

Adding to 21253603 its reverse (30635212), we get a palindrome (51888815).

The spelling of 21253603 in words is "twenty-one million, two hundred fifty-three thousand, six hundred three".