21303203135561 has 2 divisors, whose sum is σ = 21303203135562. Its totient is φ = 21303203135560.

The previous prime is 21303203135537. The next prime is 21303203135573. The reversal of 21303203135561 is 16553130230312.

It is a happy number.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14652581081161 + 6650622054400 = 3827869^2 + 2578880^2 .

It is a cyclic number.

It is not a de Polignac number, because 21303203135561 - 2³⁰ = 21302129393737 is a prime.

It is not a weakly prime, because it can be changed into another prime (21303203134561) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10651601567780 + 10651601567781.

It is an arithmetic number, because the mean of its divisors is an integer number (10651601567781).

Almost surely, 2^{21303203135561} is an apocalyptic number.

It is an amenable number.

21303203135561 is a deficient number, since it is larger than the sum of its proper divisors (1).

21303203135561 is an equidigital number, since it uses as much as digits as its factorization.

21303203135561 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 48600, while the sum is 35.

Adding to 21303203135561 its reverse (16553130230312), we get a palindrome (37856333365873).

The spelling of 21303203135561 in words is "twenty-one trillion, three hundred three billion, two hundred three million, one hundred thirty-five thousand, five hundred sixty-one".