21206779 has 8 divisors (see below), whose sum is σ = 23212800. Its totient is φ = 19213800.

The previous prime is 21206753. The next prime is 21206791. The reversal of 21206779 is 97760212.

It is a sphenic number, since it is the product of 3 distinct primes.

It is a cyclic number.

It is not a de Polignac number, because 21206779 - 2⁵ = 21206747 is a prime.

It is a Duffinian number.

It is not an unprimeable number, because it can be changed into a prime (21206179) by changing a digit.

It is a polite number, since it can be written in 7 ways as a sum of consecutive naturals, for example, 322 + ... + 6520.

It is an arithmetic number, because the mean of its divisors is an integer number (2901600).

Almost surely, 2^21206779 is an apocalyptic number.

21206779 is a deficient number, since it is larger than the sum of its proper divisors (2006021).

21206779 is a wasteful number, since it uses less digits than its factorization.

21206779 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 6521.

The product of its (nonzero) digits is 10584, while the sum is 34.

The square root of 21206779 is about 4605.0818668076. The cubic root of 21206779 is about 276.7949974802.

The spelling of 21206779 in words is "twenty-one million, two hundred six thousand, seven hundred seventy-nine".