21307253 has 12 divisors (see below), whose sum is σ = 23539404. Its totient is φ = 19272000.

The previous prime is 21307243. The next prime is 21307271. The reversal of 21307253 is 35270312.

It can be written as a sum of positive squares in 2 ways, for example, as 19166884 + 2140369 = 4378^2 + 1463^2 .

It is not a de Polignac number, because 21307253 - 2⁸ = 21306997 is a prime.

It is a hoax number, since the sum of its digits (23) coincides with the sum of the digits of its distinct prime factors.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21307243) by changing a digit.

It is a polite number, since it can be written in 11 ways as a sum of consecutive naturals, for example, 35153 + ... + 35753.

It is an arithmetic number, because the mean of its divisors is an integer number (1961617).

Almost surely, 2^21307253 is an apocalyptic number.

It is an amenable number.

21307253 is a deficient number, since it is larger than the sum of its proper divisors (2232151).

21307253 is a wasteful number, since it uses less digits than its factorization.

21307253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 916 (or 905 counting only the distinct ones).

The product of its (nonzero) digits is 1260, while the sum is 23.

The square root of 21307253 is about 4615.9780112128. The cubic root of 21307253 is about 277.2314443208.

Adding to 21307253 its reverse (35270312), we get a palindrome (56577565).

The spelling of 21307253 in words is "twenty-one million, three hundred seven thousand, two hundred fifty-three".