21780655279 has 2 divisors, whose sum is σ = 21780655280. Its totient is φ = 21780655278.

The previous prime is 21780655243. The next prime is 21780655297. The reversal of 21780655279 is 97255608712.

It is a happy number.

Together with next prime (21780655297) it forms an Ormiston pair, because they use the same digits, order apart.

It is a strong prime.

It is a cyclic number.

It is not a de Polignac number, because 21780655279 - 2¹¹ = 21780653231 is a prime.

It is a congruent number.

It is not a weakly prime, because it can be changed into another prime (21780655219) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10890327639 + 10890327640.

It is an arithmetic number, because the mean of its divisors is an integer number (10890327640).

Almost surely, 2^21780655279 is an apocalyptic number.

21780655279 is a deficient number, since it is larger than the sum of its proper divisors (1).

21780655279 is an equidigital number, since it uses as much as digits as its factorization.

21780655279 is an evil number, because the sum of its binary digits is even.

The product of its (nonzero) digits is 2116800, while the sum is 52.

The spelling of 21780655279 in words is "twenty-one billion, seven hundred eighty million, six hundred fifty-five thousand, two hundred seventy-nine".