21667777 has 2 divisors, whose sum is σ = 21667778. Its totient is φ = 21667776.

The previous prime is 21667769. The next prime is 21667813. The reversal of 21667777 is 77776612.

It is a weak prime.

It can be written as a sum of positive squares in only one way, i.e., 21520321 + 147456 = 4639^2 + 384^2 .

It is a cyclic number.

It is not a de Polignac number, because 21667777 - 2³ = 21667769 is a prime.

It is not a weakly prime, because it can be changed into another prime (21667757) 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, 10833888 + 10833889.

It is an arithmetic number, because the mean of its divisors is an integer number (10833889).

Almost surely, 2^21667777 is an apocalyptic number.

It is an amenable number.

21667777 is a deficient number, since it is larger than the sum of its proper divisors (1).

21667777 is an equidigital number, since it uses as much as digits as its factorization.

21667777 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 172872, while the sum is 43.

The square root of 21667777 is about 4654.8659486606. The cubic root of 21667777 is about 278.7863156584.

It can be divided in two parts, 2166777 and 7, that added together give a square (2166784 = 1472²).

The spelling of 21667777 in words is "twenty-one million, six hundred sixty-seven thousand, seven hundred seventy-seven".