21780766213 has 2 divisors, whose sum is σ = 21780766214. Its totient is φ = 21780766212.

The previous prime is 21780766199. The next prime is 21780766229. The reversal of 21780766213 is 31266708712.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 17050352929 + 4730413284 = 130577^2 + 68778^2 .

It is a cyclic number.

It is not a de Polignac number, because 21780766213 - 2⁵ = 21780766181 is a prime.

It is a super-2 number, since 2×21780766213² (a number of 21 digits) contains 22 as substring.

It is a self number, because there is not a number n which added to its sum of digits gives 21780766213.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21780766913) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10890383106 + 10890383107.

It is an arithmetic number, because the mean of its divisors is an integer number (10890383107).

Almost surely, 2^21780766213 is an apocalyptic number.

It is an amenable number.

21780766213 is a deficient number, since it is larger than the sum of its proper divisors (1).

21780766213 is an equidigital number, since it uses as much as digits as its factorization.

21780766213 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 169344, while the sum is 43.

The spelling of 21780766213 in words is "twenty-one billion, seven hundred eighty million, seven hundred sixty-six thousand, two hundred thirteen".