21261264545 has 4 divisors (see below), whose sum is σ = 25513517460. Its totient is φ = 17009011632.

The previous prime is 21261264529. The next prime is 21261264553. The reversal of 21261264545 is 54546216212.

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 13283023504 + 7978241041 = 115252^2 + 89321^2 .

It is a cyclic number.

It is not a de Polignac number, because 21261264545 - 2⁴ = 21261264529 is a prime.

It is a junction number, because it is equal to n+sod(n) for n = 21261264499 and 21261264508.

It is an unprimeable number.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 2126126450 + ... + 2126126459.

It is an arithmetic number, because the mean of its divisors is an integer number (6378379365).

Almost surely, 2^21261264545 is an apocalyptic number.

It is an amenable number.

21261264545 is a deficient number, since it is larger than the sum of its proper divisors (4252252915).

21261264545 is an equidigital number, since it uses as much as digits as its factorization.

21261264545 is an evil number, because the sum of its binary digits is even.

The sum of its prime factors is 4252252914.

The product of its digits is 115200, while the sum is 38.

The spelling of 21261264545 in words is "twenty-one billion, two hundred sixty-one million, two hundred sixty-four thousand, five hundred forty-five".