21081253 has 8 divisors (see below), whose sum is σ = 21420000. Its totient is φ = 20744688.

The previous prime is 21081217. The next prime is 21081259. The reversal of 21081253 is 35218012.

It is a sphenic number, since it is the product of 3 distinct primes.

It is not a de Polignac number, because 21081253 - 2²¹ = 18984101 is a prime.

It is a Duffinian number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21081259) 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 7 ways as a sum of consecutive naturals, for example, 41163 + ... + 41671.

It is an arithmetic number, because the mean of its divisors is an integer number (2677500).

Almost surely, 2^21081253 is an apocalyptic number.

It is an amenable number.

21081253 is a deficient number, since it is larger than the sum of its proper divisors (338747).

21081253 is an equidigital number, since it uses as much as digits as its factorization.

21081253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1091.

The product of its (nonzero) digits is 480, while the sum is 22.

The square root of 21081253 is about 4591.4325651152. The cubic root of 21081253 is about 276.2477864731.

Adding to 21081253 its reverse (35218012), we get a palindrome (56299265).

The spelling of 21081253 in words is "twenty-one million, eighty-one thousand, two hundred fifty-three".