21255466777 has 2 divisors, whose sum is σ = 21255466778. Its totient is φ = 21255466776.

The previous prime is 21255466759. The next prime is 21255466781. The reversal of 21255466777 is 77766455212.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 20440706841 + 814759936 = 142971^2 + 28544^2 .

It is a cyclic number.

It is not a de Polignac number, because 21255466777 - 2²³ = 21247078169 is a prime.

It is not a weakly prime, because it can be changed into another prime (21255466747) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10627733388 + 10627733389.

It is an arithmetic number, because the mean of its divisors is an integer number (10627733389).

Almost surely, 2^21255466777 is an apocalyptic number.

It is an amenable number.

21255466777 is a deficient number, since it is larger than the sum of its proper divisors (1).

21255466777 is an equidigital number, since it uses as much as digits as its factorization.

21255466777 is an evil number, because the sum of its binary digits is even.

The product of its digits is 4939200, while the sum is 52.

The spelling of 21255466777 in words is "twenty-one billion, two hundred fifty-five million, four hundred sixty-six thousand, seven hundred seventy-seven".