21015253253 has 4 divisors (see below), whose sum is σ = 21036632928. Its totient is φ = 20993873580.

The previous prime is 21015253223. The next prime is 21015253267. The reversal of 21015253253 is 35235251012.

It is a semiprime because it is the product of two primes, and also a Blum integer, because the two primes are equal to 3 mod 4.

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21015253253 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 (21015253223) by changing a digit.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 10688363 + ... + 10690328.

It is an arithmetic number, because the mean of its divisors is an integer number (5259158232).

Almost surely, 2^21015253253 is an apocalyptic number.

It is an amenable number.

21015253253 is a deficient number, since it is larger than the sum of its proper divisors (21379675).

21015253253 is an equidigital number, since it uses as much as digits as its factorization.

21015253253 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 21379674.

The product of its (nonzero) digits is 9000, while the sum is 29.

The spelling of 21015253253 in words is "twenty-one billion, fifteen million, two hundred fifty-three thousand, two hundred fifty-three".