21551413777 has 2 divisors, whose sum is σ = 21551413778. Its totient is φ = 21551413776.

The previous prime is 21551413729. The next prime is 21551413783. The reversal of 21551413777 is 77731415512.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 11235152016 + 10316261761 = 105996^2 + 101569^2 .

It is a cyclic number.

It is not a de Polignac number, because 21551413777 - 2⁷ = 21551413649 is a prime.

It is not a weakly prime, because it can be changed into another prime (21551413577) by changing a digit.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10775706888 + 10775706889.

It is an arithmetic number, because the mean of its divisors is an integer number (10775706889).

Almost surely, 2^21551413777 is an apocalyptic number.

It is an amenable number.

21551413777 is a deficient number, since it is larger than the sum of its proper divisors (1).

21551413777 is an equidigital number, since it uses as much as digits as its factorization.

21551413777 is an evil number, because the sum of its binary digits is even.

The product of its digits is 205800, while the sum is 43.

The spelling of 21551413777 in words is "twenty-one billion, five hundred fifty-one million, four hundred thirteen thousand, seven hundred seventy-seven".