21503253 has 8 divisors (see below), whose sum is σ = 29446048. Its totient is φ = 13947984.

The previous prime is 21503227. The next prime is 21503263. The reversal of 21503253 is 35230512.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21503253 - 2⁸ = 21502997 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21503263) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 96751 + ... + 96972.

It is an arithmetic number, because the mean of its divisors is an integer number (3680756).

Almost surely, 2^21503253 is an apocalyptic number.

It is an amenable number.

21503253 is a deficient number, since it is larger than the sum of its proper divisors (7942795).

21503253 is a wasteful number, since it uses less digits than its factorization.

21503253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 193763.

The product of its (nonzero) digits is 900, while the sum is 21.

The square root of 21503253 is about 4637.1600144916. The cubic root of 21503253 is about 278.0789115736.

Adding to 21503253 its reverse (35230512), we get a palindrome (56733765).

The spelling of 21503253 in words is "twenty-one million, five hundred three thousand, two hundred fifty-three".