21780766247 has 2 divisors, whose sum is σ = 21780766248. Its totient is φ = 21780766246.

The previous prime is 21780766237. The next prime is 21780766291. The reversal of 21780766247 is 74266708712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21780766247 - 2²⁴ = 21763989031 is a prime.

It is a super-4 number, since 4×21780766247⁴ (a number of 42 digits) contains 4444 as substring.

It is a junction number, because it is equal to n+sod(n) for n = 21780766195 and 21780766204.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21780766237) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10890383123 + 10890383124.

It is an arithmetic number, because the mean of its divisors is an integer number (10890383124).

Almost surely, 2^21780766247 is an apocalyptic number.

21780766247 is a deficient number, since it is larger than the sum of its proper divisors (1).

21780766247 is an equidigital number, since it uses as much as digits as its factorization.

21780766247 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 1580544, while the sum is 50.

The spelling of 21780766247 in words is "twenty-one billion, seven hundred eighty million, seven hundred sixty-six thousand, two hundred forty-seven".