21015253243 has 4 divisors (see below), whose sum is σ = 21070702840. Its totient is φ = 20959803648.

The previous prime is 21015253223. The next prime is 21015253267. The reversal of 21015253243 is 34235251012.

It is a semiprime because it is the product of two primes.

It is not a de Polignac number, because 21015253243 - 2⁵ = 21015253211 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21015253223) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (19) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 27724230 + ... + 27724987.

It is an arithmetic number, because the mean of its divisors is an integer number (5267675710).

Almost surely, 2^21015253243 is an apocalyptic number.

21015253243 is a deficient number, since it is larger than the sum of its proper divisors (55449597).

21015253243 is an equidigital number, since it uses as much as digits as its factorization.

21015253243 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 55449596.

The product of its (nonzero) digits is 7200, while the sum is 28.

The spelling of 21015253243 in words is "twenty-one billion, fifteen million, two hundred fifty-three thousand, two hundred forty-three".