21780942553 has 2 divisors, whose sum is σ = 21780942554. Its totient is φ = 21780942552.

The previous prime is 21780942511. The next prime is 21780942637. The reversal of 21780942553 is 35524908712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 16747465744 + 5033476809 = 129412^2 + 70947^2 .

It is a cyclic number.

It is not a de Polignac number, because 21780942553 - 2⁹ = 21780942041 is a prime.

It is not a weakly prime, because it can be changed into another prime (21780946553) 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 as a sum of consecutive naturals, namely, 10890471276 + 10890471277.

It is an arithmetic number, because the mean of its divisors is an integer number (10890471277).

Almost surely, 2^21780942553 is an apocalyptic number.

It is an amenable number.

21780942553 is a deficient number, since it is larger than the sum of its proper divisors (1).

21780942553 is an equidigital number, since it uses as much as digits as its factorization.

21780942553 is an odious number, because the sum of its binary digits is odd.

The product of its (nonzero) digits is 604800, while the sum is 46.

The spelling of 21780942553 in words is "twenty-one billion, seven hundred eighty million, nine hundred forty-two thousand, five hundred fifty-three".