21563253 has 40 divisors (see below), whose sum is σ = 33988416. Its totient is φ = 13608000.

The previous prime is 21563249. The next prime is 21563257. The reversal of 21563253 is 35236512.

21563253 is a `hidden beast` number, since 21 + 5 + 632 + 5 + 3 = 666.

It is an interprime number because it is at equal distance from previous prime (21563249) and next prime (21563257).

It is not a de Polignac number, because 21563253 - 2² = 21563249 is a prime.

It is a Harshad number since it is a multiple of its sum of digits (27).

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21563257) by changing a digit.

It is a polite number, since it can be written in 39 ways as a sum of consecutive naturals, for example, 142728 + ... + 142878.

Almost surely, 2^21563253 is an apocalyptic number.

It is an amenable number.

21563253 is a deficient number, since it is larger than the sum of its proper divisors (12425163).

21563253 is a wasteful number, since it uses less digits than its factorization.

21563253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 247 (or 238 counting only the distinct ones).

The product of its digits is 5400, while the sum is 27.

The square root of 21563253 is about 4643.6249848583. The cubic root of 21563253 is about 278.3373103125.

Adding to 21563253 its reverse (35236512), we get a palindrome (56799765).

The spelling of 21563253 in words is "twenty-one million, five hundred sixty-three thousand, two hundred fifty-three".