21320253 has 10 divisors (see below), whose sum is σ = 31848894. Its totient is φ = 14213448.

The previous prime is 21320239. The next prime is 21320267. The reversal of 21320253 is 35202312.

It is an interprime number because it is at equal distance from previous prime (21320239) and next prime (21320267).

It can be written as a sum of positive squares in only one way, i.e., 19686969 + 1633284 = 4437^2 + 1278^2 .

It is not a de Polignac number, because 21320253 - 2⁸ = 21319997 is a prime.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21320203) by changing a digit.

It is a polite number, since it can be written in 9 ways as a sum of consecutive naturals, for example, 131526 + ... + 131687.

Almost surely, 2^21320253 is an apocalyptic number.

It is an amenable number.

21320253 is a deficient number, since it is larger than the sum of its proper divisors (10528641).

21320253 is an equidigital number, since it uses as much as digits as its factorization.

21320253 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 263225 (or 263216 counting only the distinct ones).

The product of its (nonzero) digits is 360, while the sum is 18.

The square root of 21320253 is about 4617.3859487810. The cubic root of 21320253 is about 277.2878144226.

Adding to 21320253 its reverse (35202312), we get a palindrome (56522565).

The spelling of 21320253 in words is "twenty-one million, three hundred twenty thousand, two hundred fifty-three".