21166779 has 16 divisors (see below), whose sum is σ = 30343680. Its totient is φ = 13082400.

The previous prime is 21166763. The next prime is 21166787. The reversal of 21166779 is 97766112.

It is not a de Polignac number, because 21166779 - 2⁴ = 21166763 is a prime.

It is not an unprimeable number, because it can be changed into a prime (21166799) by changing a digit.

It is a polite number, since it can be written in 15 ways as a sum of consecutive naturals, for example, 1272 + ... + 6629.

It is an arithmetic number, because the mean of its divisors is an integer number (1896480).

Almost surely, 2^21166779 is an apocalyptic number.

21166779 is a deficient number, since it is larger than the sum of its proper divisors (9176901).

21166779 is a wasteful number, since it uses less digits than its factorization.

21166779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 7970.

The product of its digits is 31752, while the sum is 39.

The square root of 21166779 is about 4600.7367888198. The cubic root of 21166779 is about 276.6208586923.

It can be divided in two parts, 21166 and 779, that added together give a triangular number (21945 = T₂₀₉).

The spelling of 21166779 in words is "twenty-one million, one hundred sixty-six thousand, seven hundred seventy-nine".