21780655243 has 2 divisors, whose sum is σ = 21780655244. Its totient is φ = 21780655242.

The previous prime is 21780655229. The next prime is 21780655279. The reversal of 21780655243 is 34255608712.

It is a weak prime.

It is a cyclic number.

It is not a de Polignac number, because 21780655243 - 2¹³ = 21780647051 is a prime.

It is a self number, because there is not a number n which added to its sum of digits gives 21780655243.

It is not a weakly prime, because it can be changed into another prime (21780655223) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10890327621 + 10890327622.

It is an arithmetic number, because the mean of its divisors is an integer number (10890327622).

Almost surely, 2^21780655243 is an apocalyptic number.

21780655243 is a deficient number, since it is larger than the sum of its proper divisors (1).

21780655243 is an equidigital number, since it uses as much as digits as its factorization.

21780655243 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 403200, while the sum is 43.

The spelling of 21780655243 in words is "twenty-one billion, seven hundred eighty million, six hundred fifty-five thousand, two hundred forty-three".