21871777 has 2 divisors, whose sum is σ = 21871778. Its totient is φ = 21871776.

The previous prime is 21871769. The next prime is 21871783. The reversal of 21871777 is 77717812.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 19633761 + 2238016 = 4431^2 + 1496^2 .

It is a cyclic number.

It is not a de Polignac number, because 21871777 - 2³ = 21871769 is a prime.

It is not a weakly prime, because it can be changed into another prime (21871727) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 10935888 + 10935889.

It is an arithmetic number, because the mean of its divisors is an integer number (10935889).

Almost surely, 2^21871777 is an apocalyptic number.

It is an amenable number.

21871777 is a deficient number, since it is larger than the sum of its proper divisors (1).

21871777 is an equidigital number, since it uses as much as digits as its factorization.

21871777 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 38416, while the sum is 40.

The square root of 21871777 is about 4676.7271675820. The cubic root of 21871777 is about 279.6584994763.

The spelling of 21871777 in words is "twenty-one million, eight hundred seventy-one thousand, seven hundred seventy-seven".