21351212305 has 16 divisors (see below), whose sum is σ = 27326633040. Its totient is φ = 15958853632.

The previous prime is 21351212297. The next prime is 21351212359. The reversal of 21351212305 is 50321215312.

It can be written as a sum of positive squares in 8 ways, for example, as 31708161 + 21319504144 = 5631^2 + 146012^2 .

It is not a de Polignac number, because 21351212305 - 2³ = 21351212297 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21351212305.

It is an unprimeable number.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 905110 + ... + 928399.

It is an arithmetic number, because the mean of its divisors is an integer number (1707914565).

Almost surely, 2^21351212305 is an apocalyptic number.

It is an amenable number.

21351212305 is a deficient number, since it is larger than the sum of its proper divisors (5975420735).

21351212305 is a wasteful number, since it uses less digits than its factorization.

21351212305 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 1833668.

The product of its (nonzero) digits is 1800, while the sum is 25.

Adding to 21351212305 its reverse (50321215312), we get a palindrome (71672427617).

The spelling of 21351212305 in words is "twenty-one billion, three hundred fifty-one million, two hundred twelve thousand, three hundred five".