21172253 has 2 divisors, whose sum is σ = 21172254. Its totient is φ = 21172252.

The previous prime is 21172243. The next prime is 21172273. The reversal of 21172253 is 35227112.

It is a happy number.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 18472804 + 2699449 = 4298^2 + 1643^2 .

It is a cyclic number.

It is not a de Polignac number, because 21172253 - 2⁶ = 21172189 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21172223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10586126 + 10586127.

It is an arithmetic number, because the mean of its divisors is an integer number (10586127).

Almost surely, 2^21172253 is an apocalyptic number.

It is an amenable number.

21172253 is a deficient number, since it is larger than the sum of its proper divisors (1).

21172253 is an equidigital number, since it uses as much as digits as its factorization.

21172253 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 840, while the sum is 23.

The square root of 21172253 is about 4601.3316550755. The cubic root of 21172253 is about 276.6447025353.

Adding to 21172253 its reverse (35227112), we get a palindrome (56399365).

The spelling of 21172253 in words is "twenty-one million, one hundred seventy-two thousand, two hundred fifty-three".