21331777 has 2 divisors, whose sum is σ = 21331778. Its totient is φ = 21331776.

The previous prime is 21331729. The next prime is 21331781. The reversal of 21331777 is 77713312.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 14409616 + 6922161 = 3796^2 + 2631^2 .

It is a cyclic number.

It is not a de Polignac number, because 21331777 - 2¹⁵ = 21299009 is a prime.

It is not a weakly prime, because it can be changed into another prime (21331477) 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, 10665888 + 10665889.

It is an arithmetic number, because the mean of its divisors is an integer number (10665889).

Almost surely, 2^21331777 is an apocalyptic number.

It is an amenable number.

21331777 is a deficient number, since it is larger than the sum of its proper divisors (1).

21331777 is an equidigital number, since it uses as much as digits as its factorization.

21331777 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 6174, while the sum is 31.

The square root of 21331777 is about 4618.6336724187. The cubic root of 21331777 is about 277.3377651933.

The spelling of 21331777 in words is "twenty-one million, three hundred thirty-one thousand, seven hundred seventy-seven".