21253105261 has 4 divisors (see below), whose sum is σ = 21771473724. Its totient is φ = 20734736800.

The previous prime is 21253105231. The next prime is 21253105273. The reversal of 21253105261 is 16250135212.

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

It can be written as a sum of positive squares in 2 ways, for example, as 2316593161 + 18936512100 = 48131^2 + 137610^2 .

It is a cyclic number.

It is not a de Polignac number, because 21253105261 - 2¹¹ = 21253103213 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 (21253105231) 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, 259184170 + ... + 259184251.

It is an arithmetic number, because the mean of its divisors is an integer number (5442868431).

Almost surely, 2^21253105261 is an apocalyptic number.

It is an amenable number.

21253105261 is a deficient number, since it is larger than the sum of its proper divisors (518368463).

21253105261 is an equidigital number, since it uses as much as digits as its factorization.

21253105261 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 518368462.

The product of its (nonzero) digits is 3600, while the sum is 28.

The spelling of 21253105261 in words is "twenty-one billion, two hundred fifty-three million, one hundred five thousand, two hundred sixty-one".