21521253 has 32 divisors (see below), whose sum is σ = 32256000. Its totient is φ = 12678336.

The previous prime is 21521251. The next prime is 21521257. The reversal of 21521253 is 35212512.

It is not a de Polignac number, because 21521253 - 2¹ = 21521251 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21521251) 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 31 ways as a sum of consecutive naturals, for example, 108048 + ... + 108246.

It is an arithmetic number, because the mean of its divisors is an integer number (1008000).

Almost surely, 2^21521253 is an apocalyptic number.

It is an amenable number.

21521253 is a deficient number, since it is larger than the sum of its proper divisors (10734747).

21521253 is a wasteful number, since it uses less digits than its factorization.

21521253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 321.

The product of its digits is 600, while the sum is 21.

The square root of 21521253 is about 4639.1004515962. The cubic root of 21521253 is about 278.1564816108.

Adding to 21521253 its reverse (35212512), we get a palindrome (56733765).

The spelling of 21521253 in words is "twenty-one million, five hundred twenty-one thousand, two hundred fifty-three".