21306251345 has 4 divisors (see below), whose sum is σ = 25567501620. Its totient is φ = 17045001072.

The previous prime is 21306251341. The next prime is 21306251363. The reversal of 21306251345 is 54315260312.

It is a happy number.

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 10800821329 + 10505430016 = 103927^2 + 102496^2 .

It is a cyclic number.

It is not a de Polignac number, because 21306251345 - 2² = 21306251341 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21306251341) 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, 2130625130 + ... + 2130625139.

It is an arithmetic number, because the mean of its divisors is an integer number (6391875405).

Almost surely, 2^21306251345 is an apocalyptic number.

It is an amenable number.

21306251345 is a deficient number, since it is larger than the sum of its proper divisors (4261250275).

21306251345 is an equidigital number, since it uses as much as digits as its factorization.

21306251345 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 4261250274.

The product of its (nonzero) digits is 21600, while the sum is 32.

The spelling of 21306251345 in words is "twenty-one billion, three hundred six million, two hundred fifty-one thousand, three hundred forty-five".