21253205344409 has 4 divisors (see below), whose sum is σ = 21257127329040. Its totient is φ = 21249283359780.

The previous prime is 21253205344381. The next prime is 21253205344457. The reversal of 21253205344409 is 90444350235212.

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-21253205344409 is a prime.

It is a Duffinian number.

It is a self number, because there is not a number n which added to its sum of digits gives 21253205344409.

It is not an unprimeable number, because it can be changed into a prime (21253205344909) 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, 1960984187 + ... + 1960995024.

It is an arithmetic number, because the mean of its divisors is an integer number (5314281832260).

Almost surely, 2^{21253205344409} is an apocalyptic number.

It is an amenable number.

21253205344409 is a deficient number, since it is larger than the sum of its proper divisors (3921984631).

21253205344409 is an equidigital number, since it uses as much as digits as its factorization.

21253205344409 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 3921984630.

The product of its (nonzero) digits is 1036800, while the sum is 44.

The spelling of 21253205344409 in words is "twenty-one trillion, two hundred fifty-three billion, two hundred five million, three hundred forty-four thousand, four hundred nine".