21501253 has 2 divisors, whose sum is σ = 21501254. Its totient is φ = 21501252.

The previous prime is 21501241. The next prime is 21501281. The reversal of 21501253 is 35210512.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 20958084 + 543169 = 4578^2 + 737^2 .

It is a cyclic number.

It is not a de Polignac number, because 21501253 - 2⁹ = 21500741 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21501253.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21501203) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10750626 + 10750627.

It is an arithmetic number, because the mean of its divisors is an integer number (10750627).

Almost surely, 2^21501253 is an apocalyptic number.

It is an amenable number.

21501253 is a deficient number, since it is larger than the sum of its proper divisors (1).

21501253 is an equidigital number, since it uses as much as digits as its factorization.

21501253 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 300, while the sum is 19.

The square root of 21501253 is about 4636.9443602441. The cubic root of 21501253 is about 278.0702900088.

Adding to 21501253 its reverse (35210512), we get a palindrome (56711765).

It can be divided in two parts, 2150 and 1253, that added together give a triangular number (3403 = T₈₂).

The spelling of 21501253 in words is "twenty-one million, five hundred one thousand, two hundred fifty-three".