21780766291 has 2 divisors, whose sum is σ = 21780766292. Its totient is φ = 21780766290.

The previous prime is 21780766247. The next prime is 21780766309. The reversal of 21780766291 is 19266708712.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21780766291 - 2³³ = 13190831699 is a prime.

It is not a weakly prime, because it can be changed into another prime (21780706291) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10890383145 + 10890383146.

It is an arithmetic number, because the mean of its divisors is an integer number (10890383146).

Almost surely, 2^21780766291 is an apocalyptic number.

21780766291 is a deficient number, since it is larger than the sum of its proper divisors (1).

21780766291 is an equidigital number, since it uses as much as digits as its factorization.

21780766291 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 508032, while the sum is 49.

The spelling of 21780766291 in words is "twenty-one billion, seven hundred eighty million, seven hundred sixty-six thousand, two hundred ninety-one".